There is ongoing issue where some insiders have stuck to build 23620 or 26040
Announcing Windows 11 Insider Preview Build 26100 (Canary and Dev Channels) | Windows Insider Blog
[IMPORTANT NOTE] We are investigating reports that some Windows Insiders in the Canary and Dev Channels are stuck on Build 26040 or Build 23620. The investigation is ongoing, however if you are impacted by this and really want to get onto the latest build in the Canary or Dev Channel today – you can download the latest ISO here and do a clean install and opt your device back into flighting in the Canary or Dev Channels.
There is one workaround that some users have find help on this issue.
Cannot upgrade from 26040.1000 Canary Build "Edit" There is a fix I - Microsoft Community