Teams has been phasing out Wiki support from June 2023 and will be fully deprecated in January 2024.
You can still access and edit existing wikis, but you are no longer be able to create new wikis in Teams channels.
If you have existing Wiki's, we would recommend you move these across to OneNote as soon as possible by following this link and the instructions under 'Export a Wiki to a OneNote notebook'.
Teams Wiki is Going...