I have some clients complaining that they cannot access like watsapp or sometimes even websites. Client has an active internet connection but these services just all of the sudden are a problem. Where do i start checking? on the Mikrotik firewall rules or advise if you have this experience too and what was done to restore.
It always DNS... seriously, which DNS servers are they using?
Check IPv4 and IPv6 independently. Check if it's a MTU/MSS issue. Oh, and check DNS 
DNS was the issue, thank you for your feedback. Much appreciated.
Issue resolved, thank you and much appreciated. Primary DNS was quad9 and sec-google dns. Client now able to resolve.