I have the same issue, I bought all attachments. I tried private and public and I tried different modes, it's refusing to pop. I tried putting each gun in holster as I was buying instead of quickly swapping them. Even bought all in one control game and nothing

Maybe it could be related to removal of one of the sight attachments? https://discord.com/channels/1013740143003324487/1013814110389014569/1382400880418095205

(unknown user mentioned) sorry for sudden ping but I saw you were gonna check if it works back then, did you end up doing it? I'm just trying to see if I'm missing something. It seems like this has been broken since May, last achiever on playstation is around May 20th.

According to exhophase no one on steam got decked out achievement since April, so something definitely went wrong around then

Here is a video of me buying all attachments, I didn't get the trophy. I have finished the match, also keep in mind I bought all these weapons and attachments in bomb defusal too, 1 per round with all attachments. This was in a custom TDM match, I did the same yesterday in custom Control with no luck. I hope the video can at least show if I'm doing something wrong or if I missed something, I have rewatched it and seems like I unlocked all attachments, so I assume something must be broken

As you can see I'm also holstering each weapon