sadly the tax laws bar you from going from a joint return to married filing separate after the original tax deadline of 5/17/2021. you say you already filed with the form attached so filing a second 1040 probably wouldn't solve your issue. see below about filing the form by itself. if you mailed in your return there's no telling if the 8379 got processed. you did nothing wrong by filing jointly in 2020. prior years have no effect on the ability to use any filing status you qualify for. as long as you were legally married to him when he died and did not remarry before year-end you qualified to file a joint return with him. you may be able to use a CPA rather than a tax lawyer.
if you live in a community property state see a pro, no need to read any of the following. the rules for allocations are different in those states than in states without those laws.
you should have received some sort of notice from the IRS about adjustments made to the 8379 allocations. if you did get such a notice try calling the phone number on it to get an explanation. if not that could indicate the 8379 didn't get processed.
before going through the expense of using a pro you have several options.
1) try calling the IRS to see if it can tell you what the issue is
800-829-1040
First choose your language.
Then 2
Then 1
Then 3
Then 2
When asked for SSN do nothing it will ask twice
Then 2
Then 4
You should then be transferred to an agent, but there is likely to be a long wait. note that you may not get through even after repeated tries. at the present, the IRS is getting more calls than it can handle
2) file form 8379 buy itself. see the instructions below for where to mail it
https://www.irs.gov/pub/irs-pdf/i8379.pdf
3) contact the IRS Tax Advocate Service to see if they can help. it's free. not honoring form 8379 would seem to indicate you did not receive fair and equitable treatment. see the website below for how to contact them. however, there is no guarantee that the TAS will take your case.
https://www.taxpayeradvocate.irs.gov/can-tas-help-me-with-my-tax-issue/
