net::ERR_HTTP2_PROTOCOL_ERROR whmcs

Hello guys, im new here.

So i have an hosting company where im using whmcs for control panel.
For VPS we use virtualizor module.
Our Panel on whmcs won’t load and after some times it give net::ERR_HTTP2_PROTOCOL_ERROR on Devtool chrome console.
Screenshot: https://i.ibb.co/9NfRdw9/proof1.jpg
I contacted virtualizor support but they say is a connection problem and it was working like 2 days a go and they say to contact cloudflare.
I don’t know what to do, alredy tried alot of things for fix but nothing.

This is what virtualizor support said:
Hi,

Sir we tried to check on your server but it seems that something is killing the load.
I got NS_BINDING_ABORTED when Virtualizor tries to load the javascript and css.
I also tried to increase the memory limit as well but it did not help.
Also tried to increase the curl timeout limit but that also did not help.
It seems a cloudflare problem or beckend problem.

Let us know.

Please help me

If you are using cloudflare for that domain/ subdomain, then:
First, try to add Cloudflare IP range to your VPS, detailed here: https://support.cloudflare.com/hc/en-us/articles/200170786-Restoring-original-visitor-IPs
You can find IP range here: https://www.cloudflare.com/ips/
Sencond, whitelist your server IP at Cloudflare. Tutorial here: https://support.cloudflare.com/hc/en-us/articles/217074967-Configuring-IP-Access-Rules

Then check if problem resolved

P/S: One more thing,did you try to use other browser, and is it work? This problem sometime happen on Firefox but it work on Chrome or Edge and vice versa.