The liquify tool will straight up not even allow you to use the brush for no reason whatsoever, and a bunch of people have the issue with no fix available.

https://community.adobe.com/t5/after-effects/after-effects-2020-liquify-tool-is-not-working/m-p/1086...
https://community.adobe.com/t5/after-effects/liquify-tool-stops-working-throughout-cc2019-project/m-...
https://community.adobe.com/t5/after-effects/liquify-issues/m-p/11044462?page=1
https://community.adobe.com/t5/after-effects/liquify-tool-not-working/m-p/11063754?page=1
https://community.adobe.com/t5/after-effects/liquify-tool/m-p/11148793?page=1