I just experienced the same issue upgrading Vertex framework from 3.6 to 4.1 with the site shaper installation of Corpway I installed back in 2014. I backed up my site, then used FTP to upgrade the files in my template folder. Upon logging back in to the admin area after clearing my cache, the template configuration page would open but it was blank, empty boxes with no text in them, just like in the OP's message. The attached file shows this.
I restored from my site backup (thank you Akeeba backup!) and then read your instructions more closely. This time, I disabled my Cloudflare and reinstalled the new files. Then cleared the cache, went back in, and now the template config page opened without any trouble. As soon as I re-enabled Cloudflare though I could no longer access the configuration page and it went back to a blank page with boxes but no text. In order to use both Cloudflare and Vertex, it seems that you have to create a rule that specifically disabled the "performance" features for the Joomla backend. The rule that worked for me looked like the second attached file.
I hope this saves somebody else some time. I sure do like having scripts and templates up to date and I am very pleased with the longevity of my Shape 5 template.
Regards,
Glen
https://www.alaskacomputerguy.com