am i a dumb plond?

first off, i'm still not a homerecording guy, so my knowledge how to handle things in reaper best is a sidewalk high above street level. thought setting a tempo change should be an easy sneas. I ain't bore you with the whole story. i did what is written in the user guide (at least i think i did) and gone searching each rabbit hole. you'll prolly guess how far i came. here's what i got. 4 acc gtr tracks (recorded prior to drums) 1 drum folder (midi) tempo marker works for the folder only. would appreciated any help. thx.

You're in Time Timebase if only the MIDI responds to tempo changes. Change it in Project Settings to Beats Timebase.

does this video help ?

thx guys, i did a work around

open the envelope lane for the tempo envelope and delete the envelope. same as a volume envelope.