USSD codes disabled

[justmeagain79]

I use the #*9900* USSD code on my phone to tweak my settings. Lately, I can't use any USSD codes at all!! Is it a carrier issue or are they stopping access to them. This is what I get now.

[alone799]

S20 ultra ussd code running don't working 

[Mgagani85]

I have the same problem, i have samsung A90 5G  also ussd code running not working.  Any help how can i solve this