Colds, flu, sinus infections, and of course Covid can cause loss of smell/taste. If nasal rinses and OTC nasal steroid sprays don't work, you can try smell therapy (which sounds a little nuts, but I'm learning that nerve damage of any kind leads to some weird symptoms). This post has a suggested smell therapy regimen:

https://www.henryford.com/blog/2022/01/regaining-sense-of-smell-and-taste-after-covid

Also, stay hydrated! If you can't taste anything, you're more likely to get dehydrated. <3