Error 503 Backend fetch failed in customer service page

[giggiwolf]

Hi,

I am currently reinstalling prestashop on a new hosting to build my site again from 0, but I am facing a lot of problems with it. The last problem that came up is the fact that when I set up the IMAP configuration in the customer service page, the website returns me the error:

Error 503 Backend fetch failed

Backend fetch failed

Guru Meditation:

XID: 386305535

Varnish cache server

From this moment I can use my website normally, except for the fact that I am unable to access the Customer Service page from the backoffice, returning me the same error I mentioned above. I tried reinstalling again ps, but the same happened after setting up the mail in the customer service page. During the installation process, I always have to click restart installation because when the installer goes at 75% (installing modules),  i get  (from the installer), the same error 503, and it asks me to redo the installation. If i redo it, it installs normally. 

I am using a performance hosting from OVH, associated with a Cloudflare pro plan. The version of Prestashop is 1.7.7.5.

I have already tried to clear the cache and enabling debug mode, but without any good result.

[giggiwolf]

I found out that my issue is related to the customer service email system. Every time I click on customer service, the system tries the dedicated imap configuration I entered, and waits for a response which goes over the varnish cache timeout, returning me a 503 error. What I need to do is modify the imap parameters without accessing the customer service page. I would like to do it via ftp, but i do not know the related file to modify