solved: answer in comments. short answer is Piper needed to be installed.
I installed solaar.
It calls my mouse a m500s. In Solaar i set key/button diversion (there are 2 drop down menus) one i set to forward button the other i set to regular. This causes one of the buttons on the side of the mouse to act as the forward button on a web browser.
key/button actions drop down menus (2 drop down menus) I set to
back button and mouse back button.
when i run
xev -event mouse | grep -b2 button
4319-ButtonPress event, serial 25, synthetic NO, window 0x3000001,
4381- root 0x1e5, subw 0x3000002, time 13605046, (43,38), root:(75,102),
4452: state 0x10, button 9, same_screen YES
4494-
4495-EnterNotify event, serial 25, synthetic NO, window 0x3000001,
4708-ButtonRelease event, serial 25, synthetic NO, window 0x3000001,
4772- root 0x1e5, subw 0x3000002, time 13605214, (43,38), root:(75,102),
4843: state 0x10, button 9, same_screen YES
4885-
4886-LeaveNotify event, serial 25, synthetic NO, window 0x3000001,
that is the result if I hit the forward button on the side of the mouse in the test window. but no result of hitting the other side button (the back button).
I know that the o/s isn't recognizing the button press but not sure how to get linux mint to recognize the pressing of the button.
any thoughts on how to fix this issue?