Error 503 Backend fetch failed Guru Meditation Varnish Cache Server

[sitopro4]

Good morning,
I have a problem. I'm using a plugin named "Duplicator" for make a backup but it gets this error.
how can i resolve it?

 

[Dead-i]

Hi,

There is a limit on the amount of time your PHP script can execute for. If your script takes too long to execute, you will see the 503 Backend Fetch Failed message.

Thank you,

 

[sitopro4]

so how can I fix it? Have i to edit the htaccess file? Or can you disable the varnish?

Thanks

 

[sitopro4]

sorry but I really need to resolve this issue as soon as possible. Thanks.