Connection lost. Saving has been disabled

Hello all,

When I was trying to add a new post to the site, every time I try, I got the same error message. “Connection lost. Saving has been disabled.”

I need to wait about 5-10 mins to save the post. The error message disappears for just 20-30 secs, then re-appear again. And also, when I got this error message, I cannot access anywhere in the site, and also cannot open my website. But when I try to access from another logged out computer or another logged out browser, I can see the website.

It is not about my computer or connection because our other writes experience this problem from different locations and computers. Please help me, I am going crazy. ??

My website is: https://www.frpnet.net