100% discount for certification no longer available

Hi. I linked my private account with my work account to claim 100% discount on the DA-100 certification exam (my employer is a large IT company that has some partnership with Microsoft). I successfully claimed the discount a few weeks ago, according to a text that showed up it was valid until June 2022 (not sure about the exact date, but I'm confident it was several months ahead). I continued on the examregistration.microsoft.com and took a look into available timeslots, but in the end didn't book any; a few weeks have passed and I tried to schedule my exam today. But the discount is no longer there. I do receive all verification codes sent to my work address, but they don't work. I tried it in Chrome and Edge, so I doubt it's anything browser-related. I also disconnected my private account and my work account and linked them again - no effect. Is there anything I can do to troubleshoot that?