"Updating failed" error

[Admin]

Do you use Cloudflare with Flexible SSL? I believe it tends to cause this issue. Switching to Full SSL would solve that:

How to setup Full SSL with Cloudflare

By default, Cloudflare uses a system called “Flexible SSL”. In this system, Cloudflare secures the connection between your visitors and Cloudflare, but not the connection between Cloudflare and your website. Not only is this less secure, some websites (notably WordPress) have trouble detecting whether HTTPS is in use, causing all sorts of issues. The best way to resolve this is by using Full SSL in Cloudflare. This way, the connection between Cloudflare and your website is encrypted, and your w…