I need major help.

I’ve had my depop account for over 5 years and have NEVER had a problem selling on depop. Then, I sell one shirt from free people NWOT for like 20 bucks, and once it gets delivered the girl claims that it says the package was delivered but never arrived for her. Depop sent me that notification, and I rebutted because I have the USPS receipt and everything saying it was confirmed dropped off. I am a 5 star seller and have sold over 100 items! All of the sudden, MY ACCOUNT GETS SUSPENDED!! I obviously contact Depop, and this was their response!! Guys!! Seriously what do I do! I have money in that account and a shirt I still need to ship! This is devastating and so wrong! What should I do next?