1995 Buick Regal wont shift out of first gear

There are several reasons why you transmission won't shift out of 1st.

1) The clutch plates have burned up
2) Some of the rubber seals inside of the valve body are
leaking and not allowing the fluid to circulate correctly.
3) Dirt or dibre has clogged some of the passages inside
of the valve body
4) Your power control module is failing. (Least likely)

Your only recourse is to have the transmission tested by a professional.