To bring together several threads here:
Firstly, this is probably a bug in Grammarly, because a definite article ("the") would never be used before a pronoun. It probably doesn't have "thou" in its dictionary (since it is never used in modern English), so may be guessing wrongly that it's a noun.
However, the sentence is grammatically incorrect, because "thou" is (or was) both singular and subjective (also called "nominative"; like "I" and "he", as opposed to the objective/accusative "me" and "him").
If "all of X" is intended to refer to multiple people, you would need to use a plural pronoun, so it would need to be "all of you" instead. ("You" is used for both subject and object, so that distinction is not important in this case.)
Alternatively, if "all of X" is intended to refer to "the totality of X", it would need to be an objective pronoun, so it would be "all of thee". (The resulting sentence is odd, but not impossible; perhaps: "I didn't just lie to thy [your] face, I lied to all of thee".)
If we take away the "all of" to remove this complication, we can write some sample sentences with both "thou" and "thee":
- I lied to thee
- Thou lied to me
However, these possibly still aren't sentences that would have been spoken at a time and place that used "thou" and "thee" regularly, as the verb would also have taken different forms based on the pronoun.