I have a 96 concorde with automatic transmission.It won't shift into the last gear.Has transmission fluid at the right level.What can cause these issues?

Did you find the problem?
Today my 1997 concord, 50K miles, didn't up shift.
I think it was in second gear. I headed back home to take my truck and it started shifting again.
Drove it another sixty miles with no problems.
Fluid level, OK.
I am thinking a fluid change may help.

i have a 95 concorde and won't shift out of 2nd gear can you help me with this