Unless the lack of a "bump" is causing some functional problem, audio, sensory, or otherwise do not be concerned.
Especially if the keyboard is working....
AKA "If it ain't broke then don't fix it".
After awhile you will probably no longer notice the lack of the "bump".
Otherwise, if the lack of a bump is a problem, then there may be some debris or other issue with Enter key.
Which means possibly having to pop off the cover and doing some cleaning.
Refer to the keyboard's User Guide/Manual regarding maintenance and cleaning, Be careful not to void any remaining warranties.