Is this a composite wall or a complex profile wall?
Composite walls you can change the materials in the info box or the wall settings dialogue for the reference side, other side and wall ends.
Complex profile walls only let you change the wall end materials.
You must edit the side materials in the profile editor and re-save your profile.
Please go to the profile link at the top of the forum and add your machines specs, operating system and Archicad version to your signature.
These can sometime affect the answers that you get as there are many differences between versions and operating systems.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11