Premium plugin won’t work.

I recently purchased the premium SF Cache plugin and its worked fine for about a month then disappeared. So I uploaded it again and its done the same. Ive tried it on a few different sites and its just won’t stick.

I’ll upload it and activate. Then its fine for 5 minutes maybe even a day then it’s gone?

I’m currently using Divi Theme by elegant themes and I’ve removed all other plugins to avoid any compatibility issues.

Any help would be greatly appreciated.