please take a look at the suggested content:
https://support.pega.com/question/skincss-issues-upgrade-81
https://support.pega.com/question/getting-messed-page-app-studio-not-able-work-app-studio
https://support.pega.com/question/pega-developer-portal-ui-distorted-pega-717
Please clarify your Pega version -can you confirm you are working on an Enterprise Edition rather than Community Edition?
Check the cache and the logs for the error that is seen.
Static content troubleshooting FAQs
The StaticContent table grows based on count of harnesses, skins, and the applications in use.
Clearing the app cache using the TRUNCATE command is fine – this is a functionality that is offered in Pega Labs and used quite often.
@SunilkKumarK truncate the static content table - see Designer Studio is not loading properly | Support Center