Got CP05A notice for 2019 refund back in November, provided the required information in December but have still not received refund. Apart from contacting the IRS about the 2019 return (am actively trying, but their lines are constantly busy), should I continue with my 2020 taxes or wait until I hear back about my 2019 return.
You should file your 2020 return in a timely manner, whether or not you hear back from the IRS by April 15th (or whatever date the due date turns out to be).
The processing of returns from year to year is largely independent - the IRS will expect you to file your 2020 return even if your 2019 CP05A is not resolved.
I suppose you have seen this, but here is the IRS page on the CP05A.
You should file your 2020 return in a timely manner, whether or not you hear back from the IRS by April 15th (or whatever date the due date turns out to be).
The processing of returns from year to year is largely independent - the IRS will expect you to file your 2020 return even if your 2019 CP05A is not resolved.
I suppose you have seen this, but here is the IRS page on the CP05A.