I have a strange problem recently, part of the PCs mainly are ESXI VM cannot ping gateway(RB2011UAS) they show time out. But they can go internet through gateway. ICMP packet has already set accept and I can see there is packet flow. PCS are connect SG300 layer 3 switch and then connect RB2011UAS go out internet
/tool sniffer quick ip-protocol=icmp should tell you whether the Mikrotik responds to the pings (and where it sends the responses). If there are no responses, something is wrong with Mikrotik firewall, so follow the hint in my automatic signature below. If Mikrotik does respond, the issue is somewhere else.