SKUID Theme Composer Issue - Cannot read property 'iconsets' of undefined

We just moved our code from Dev to UAT and found none of the pages are loading as expected and seeing issue saying skuid theme.css  cannot be found.

I went and updated all the outdated themes, still no luck. I tried to open the theme we are using on all the pages but it does and load and showing the message ‘Loading theme compose’. I did an inspect and found this message ‘Cannot read property ‘iconsets’ of undefined’ in the console.

Below is the message in console for all the pages:
Failed to load resource: the server responded with a status of 404 (Not Found) - skuidtheme.css.

But all these pages are working fine in dev sandbox.