I am legally married,however have been sep from my spouse for going on 4 years.I have been filing married filing separately and the IRS kept my refund for his obligation.

The IRS took my refund and applied it to his previous tax obligation. The tax obligation was his only, why would they or how could they even legally do this? I am married, yes, but I have been separated for 4 years. It is not fair that they took my refund to pay for his obligation. How do I fight this? Or can I even fight this? Everytime I call the IRS ever since the update shows they've applied my refund they keep saying for me to wait the 21 days, EVEN THOUGH here we are, 21 days later and my refund status remains that they've applied it to a previous tax obligation, clearly I've always filed correctly and have never received such obligation letter, only he has and they had suspended his obligation due to the pandemic but now that the pandemic is more in control I guess the payment resumed, so why are they going after MY taxes if it's my spouse's situation? I have been trying to divorce them for FOUR years, we've been separated for FOUR years, I live in a whole other state than them at this point. What can I do?? Please help.