Suppose you were chatting with your English teacher online via Skype or the like, and then it suddenly was disconnected, which was more likely your connection problem and not your teacher's, furthermore, you reconnected it and you said:
"I think that is my network provider's connection problem, not yours."
"I think that was my network provider's connection problem, not yours."
Regarding parallelism, sentence #1 complies with the rule, but I believe it is more appropriate to use past helping verb like in sentence #2.
Which is correct between them?