varnish cache resetting after 300 seconds

Hi, I am running varnish, newspaper on an apache server. My varnish cahce is resetting after 300 seconds. I have disbaled all plugins and it still resets.

I spoke to my host and they think it is to do with the theme. The response is below.

Is there anything in the theme that would make my varnish cache reset after 300 seconds? Is there any testing I can do to find out the cause?

thanks

Re: Varnish not caching properly
Message #: 144644728
Time: 2018-01-20 12:35:18

Hello,

Thanks for contacting DreamHost. Sorry to hear about the problems you
have been experiencing. I did some testing and it appears the something
installed within WordPress is causing the varnish cache to expire after
300 seconds. I tested this by creating a basic HTML file and then running
a curl command to see the varnish cache time listed.

$ curl -I https://www.homeremedyhacks.com/dh.html
HTTP/2.0 200
date:Sat, 20 Jan 2018 20:33:33 GMT
content-type:text/html
content-length:0
server:Apache
last-modified:Sat, 20 Jan 2018 20:26:40 GMT
etag:”0-5633b03b9c974″
x-cacheable:YES
accept-ranges:bytes
x-varnish:748103202 748102147
age:405
via:1.1 varnish

As you can see above the cache went paste 300 to 405. It could be a
plugin or the theme itself. Check to make sure to see if there is some
sort of internal plugin or theme caching enabled and then disable it.

Please feel free to contact us if you have any additional questions.

Thanks!
John R