Transmission acts like it is in neutral will not drive

Signal416

My 2001 4 runner was driving on the highway and the automatic transmission all of a sudden appeared to be in neutral. I tried shifting it to a different gear but it did not change. When I pulled over I tried the transfer case and shifted from high to low and back, still it acted like it is in neutral. The park works but when shifted to a gear no movement the vehicle reacts like it is in neutral. Looked at the transmission linkage and it moves and appears to be ok. I checked the fluid level in the transmission and it is ok, no change in colour.