If you're not receiving reverse shells or Metasploit exploits are not creating sessions:
This is often caused either by incorrect settings (so double check this first!), or by using a VM, but running the VPN on your host machine. If the VPN is connected on your host and the VM is connected through the host, then you do have a route into the network and can access machines: VM -> Host -> TryHackMe Network. Your reverse shells don't know about that extra step though: as far as they're concerned, your TryHackMe IP belongs to your host -- not the VM. When the reverse shell is sent, it gets sent back to the host, but goes no further -- it has no reason to, because it's already reached its destination. Metasploit (or any other listener), however, is inside the VM, and thus will never receive the shell because it already got stopped at the host.
If the connection is slow, or there is a high degree of latency:
First check your own connection to your home network -- are you a long way away from the router? Is your internet connection usually noticably faster than it is when connecting to the TryHackMe network? If so, go to the TryHackMe Access page and ensure that your chosen VPN server is the one closest to you geographically. If it isn't, switch server and regenerate (then redownload) your connection pack.
- Are you running OpenVPN as Administrator on Windows, or root on Linux?
Are you still able to connect to sites such as Google whilst using the OpenVPN?
- If not, try switching servers and regenerating (then re-downloading) your VPN configuration pack on the TryHackMe Access page.
- Some countries block OpenVPN traffic, e.g. China, Egypt, North Korea, etc.
- Check if you live in one of these countries. If you do then you will not currently be able to legally connect to the TryHackMe network via OpenVPN.