Hi! There is a known issue of this:
https://flightsimulator.zendesk.com/hc/en-us/articles/360016027399-KNOWN-ISSUES-Last-modified-Feb-16-2021-
Also, there is a topic here:
https://forums.flightsimulator.com/t/addons-in-community-appear-as-not-installed-in-content-manager-after-updating-to-1-15-7-0-and-world-update-iv-although-they-are-installed/390491