My mashup are not opening and they keep on loading continuously

Hello @unknown 

Can you please share some of the further details?

1) Have you made any recent changes in the system after which you are facing the issue?

2) Is there any custom extension presnt in your application?

There are certain things you can try to narrow down the issues

1) Check if index.html file is missing from the following path \ThingworxFoundation\tomcat\apache-tomcat-9.0.43\webapps\Thingworx\Builder

2) Builder location should not contain unwanted files 

3)In case of error on mashup loading on edit check if css and js file used in index.html files exists or not with correct name of the file

 you can also refer the following article for your reference

https://www.ptc.com/en/support/article/CS356827