@B2Pi
As far as I know, SketchUcation Tools does not require access to edg3d.io .
Currently there are 2 IP addresses which are used by different parts of the Tools: 144.76.69.227 and 178.63.47.155
Plus some functions (image, javascript, css, and .rbz file downloads) are using the Amazon AWS CloudFront CDN. The CDN URLs are:
https://pluginstatic.sketchucation.com
http://pluginstatic.sketchucation.com
https://pluginrepo.sketchucation.com
http://pluginrepo.sketchucation.com
If the access to https://pluginrepo.sketchucation.com/ and it's sub folders is blocked, it might cause the error message you mentioned.
Let us know if unblocking these URLs helped or not.