I have 700 customers and the Mikrotik Proxy failed over and over again after 2 days.
I went back to squid.
I am not alone with this, others have reported it. I do not know how to fix it.
I would not use the Mikrotik Proxy (yet) on a network your size.
I’m going to second Equis’s comments, web proxy is unreliable imho at the moment.
If a mikrotik rep tells us they’ve fixed it I’ll try again but for now it’s pretty much useless for any long term use.
I had the same problem, it started working again after I flushed the DNS cache. At first I tried pointing it to my squid as a parent proxy. Now I’m using the nat rule directly to my squid/dns server combo. Haven’t had a problem with that setup in months.