Did you look to see if the UBS BBCode is still enabled? If the UBS BBCode is disabled, it will not render anywhere.
Admin CP >> Content >> BB Code >> Custom BB codes >>
View attachment 9682
If it is disabled, enable it and then go back to the post, edit it, then save it and it should render.
If is is enabled, disable it, then re-enable it and then go back to the post, edit it, then save it and it should render.
If it is now working in the Post, then go to your Custom BBCode Page and see if its working there (since it wasn't working anywhere, it should be working now).