RE: Journal Creation got an Financial dimension does not exists Ax 2012 R3
Let'e have a look in below areas in UAT which could make a difference compared to PRD environment.
-- If any dimension value is set to 'Suspended'.
-- Or if any dimension value is set with 'Active from' and 'Active to' date where 'Active to' date is already over as of today's date.
-- How you structured your account structure in UAT? Is it different than PRD? Set the same structure in UAT then.
-- Have you added all possible financial dimension nodes in the account structure!
-- If dimension value is set to any specific legal entity and not applicable in the entity where you are trying to use it in journal. Example below.

-- Check the delimiter as asked by Chanaphat. You can do a small trick on this too especially when no other user is using UAT. Just change the delimiter in GL parameters form; save it. Then again change it back to it's original and save it.
-- After that try to upload the journal lines again and see if this time it's working.
Regards,
Sourav