TL:DR; The answer is past continuous
You sentence should read:
Two days ago, I tried to order a book but could not pay because your
system was not accepting PayPal payments yet.
Edit: I have used the American Corpus) to research this answer after the fact, using the searches: "did not work", "was not working" and "did not accept"
I believe that I have given the most correct phrasing. The phrasing with "did not accept" is highly problematic because it implies that the system rejected the concept of PayPal payments and does not fit with the adverb "yet."
You can see how the phrasing of the wording "did not accept" is used in real textual examples across multiple sources on the corpus (not possible to link).
You can also see how "was not accepting" is the correct choice and is used for just such situations here. Not possible to link.
Please read this explanation to understand why. I hope this is helpful.
Why your logic is appropriate
You are correct to think that a perfect tense would be appropriate, not only because of the adverb "yet," but also because you have an action in the past at which you are only looking in terms of completion (whether something has or has not been done).
Why the present perfect (and past perfect) fail
Considering that the past perfect is only appropriate when an action is looked at in terms of completion, it does not work with time markers. In other words, you cannot say that something was done at a particular point in the past with the present perfect. The same goes with the past perfect in the sense that you need a point of reference in the past to which compare it to.
Let's break down the events
- You tried to order a book two days ago.
- At that point, you could not order it.
- You could not order it because the system wasn't working.
- The system was working after you tried to order it.
First of all, let's consider a couple of minor corrections to this sentence.
Point 1. "Two days ago" is an adverbial phrase and needs to either be placed at the end of a sentence without commas or at the start, followed by a comma ("Two days ago,...")
Point 3. If you say something didn't work, it means that particular action was attempted and failed.
Let's look at an example:
I tried to open the door, but it didn't work.
The action of opening didn't work meaning that I probably didn't have the key or the door was broken.
I tried to open the door, but it wasn't working.
My action was correct, but there was something wrong with the door.
Let's do another example, just for clarity.
Giving her flowers didn't work. She is still angry with me.
Using the verb "work" in the past simple refers to specific individual actions.
If you want to refer to a system you have to use the continuous tense because that state is continuous (in the present, this does not apply).
I couldn't do my homework last night because my computer wasn't working.
Still doubting? Would it be correct to say:
Yesterday, my computer didn't work.
(answer: no, it wouldn't be)
Alright! I hope that as a reader you are as excited as I am because now we have a identified a problematic part of the sentence that can be quickly and logically fixed.
Why past continuous is the solution
because your system did not accept/ has not accepted paypal payments yet.
Since with the verb accept we are referring to a function or action, that same rule from the verb "work" applies. You are referring to a system, which means you need to refer to it as a state of continuity in the past. So the statement needs to be rephrased to the past continuous.
Correction: because your system was not accepting paypal payments yet.
Conclusion
The complete correct sentence would be:
Two days ago, I tried to order a book but could not pay because your
system was not accepting PayPal payments yet.
Rules that apply here:
- When referring to the operation of something in the past use past continuous.
- The adverb "yet" is not problematic as it can be used in the past, present, or future.
- When referring to the operation of something in the present it doesn't matter whether you use continuous or simple tenses.
- When an action fails, you can use past simple or present perfect according to the rules of each of those tenses.
- Similarly, the past perfect can be used in with failed actions, and past perfect continuous would be suitable for systems.
Sources
Corpus of American English: https://www.english-corpora.org/coca/
Search 1: "was not working"
...is off topic, but your contact link was not working.
... it was fine except that the shower was not working correctly (Room 760) ie. the water temperature could not be controlled.
...The device simply was not working one morning. So I searched online for a replacement and thought I was...
Search 2: Did not work
I built 2 websites with SBI and they did not work. I must say it wasn't Site Build it's fault but mine ... I must say I made more money ... from Amway, Melaluca, Pre-paid legal, Primerica
Here the websites did not work because they did not do the job they were meant to do, make money. It doesn't mean that they weren't operating. It means, that the attempt of "making a website" failed.
Apple was never able to dent the Windows monopoly, so they flanked it. Windows did not work on phones and tablets so Apple created a separate OS and made it the standard for mobile devices.
In this case, the meaning of "did not work" does not mean that windows was not operating on mobile devices. In other words, it's no a question of technical problems. It means that it was not at all adapted to them.
Your enclosed URL did not work, would you be so kind to resend this to web site to us?
Meaning: The URL did not take us to where we were supposed to go. You would say the "URL was not working" if you knew you had the correct URL, but the system was down.
The major reason that the discounts did not work is because the toys were not " hot. "
Meaning: The act of using discounts did not create the desired effect.
Did not accept vs. was not accepting
Originally, some scientists did not accept its validity, believing that all habilis specimens should be assigned to either the australopithecines
...who could not log-in to a laptop because the server or the computer was not accepting their username and password. The problem should be resolved next week.