/30 has 2 useable ips (1 & 2) and you have used both of them on the routers. your system ip is no longer on that subnet. but /24 has more ip which include you system or device ip in the subnet. that is why it is unreachable in /30 and reachable in /24
thats why im wondering why the packets cant pass through if im using /30 and keep my head spinning of this. as my understanding /30 2 usable ip and it can use two routers to communicate as a gateway becasue i have another subnet defrent ip.