It is possible an ISP is blocking traffic but unlikely. In the UK they typically only block traffic under court order.
the following options could help you identify where the bottleneck is,
You can run the tracert command and use one of the ip addresses of a peer.
On windows it looks like this,
C:\>tracert 192.168.1.254
Tracing route to 192.168.1.254 over a maximum of 30 hops
---------------------------------------------------
1 2 ms 3 ms 2 ms 10.0.0.2
2 75 ms 83 ms 88 ms 10.0.0.1
3 73 ms 79 ms 93 ms 192.168.1.254
Trace complete.
This will at least show you the route between you and the peer that you could connect to is reachable, similar with
C:\Users\Admin\Desktop>tcping.exe 192.168.1.254 30303
C:\Users\Admin\Desktop>tcping.exe 192.168.1.254 30301
with the tracert output you should be able to see any hops along the way that may be congested or dropping network packets.
if you can reach the peer and getting a response back then most likely the ISP is not blocking traffic. If network packets are getting dropped along the route and your getting no response then it may indicate that something is blocking traffic.
It might be that only a specific type of traffic is being blocked such TCP/UDP on a specific port.
- You can try using a VPN connection and connecting to a different country that does not block ethereum traffic.