got ageusia without anosmia, tested negative on a COVID kit (might have slightly screwed up the procedure though) - so what's going on?

I gained ageusia (loss of taste, but my sense of smell is just fine) out of nowhere at the beginning of this month & it's still persisting.

I've already been on the most of the exact vitamins/supplements people claim can fix ageusia/deficiencies of such are associated with it (b12, vitamin E, C, CoQ10, ALA, and I think NAC was listed as well?) - the only one I haven't been on is zinc, which I finally got right back on like around/after this occurrence. But anyways - I upped the doses on the ones I've already been regularly taking just to further push things.

as for the COVID test kit - it's one of those 7 dollar ones from Walmart. I screwed it up a tiny bit in the fact that I slightly missed one of the 4 drops from the little tube thing (it didn't fully make it into the sample hole on the meter, much of it landed right beside it) - so it may render the result as unreliable + the instructions claimed that it is still recommended to take the test again 48+ hours later if negative; for precision's sake.

does anyone here know what is even up? is this likely COVID? or is it something else? and how do I fix it (aside with relying on time in hopes that my sense of taste returns?) it's driving me nuts tbh.

**I suspected that it was due to taking a probiotic in late May (acidophilus); but people on the probiotic sub claimed that it is impossible/unlikely.