Were you able to translate at all in the previous version before it started happening?
If no translations at all are coming through, I would bet that your 500.000 characters on the free limit are maxed out for this month. If that's the case, the error message itself is a bug; it should give another message back.
If they are not maxed out, let me know, I'll be able to release a version tomorrow that makes it possible to disable batch requests for DeepL and we'll see if that works for you.