If Microsoft 365 network connectivity test tool fails, whitelist required URLs and IP ranges on Firewall/Proxy, bypass the SSL Inspection, etc.
Network testers are ideal for IDing bad cabling, helping to troubleshoot network issues, estimating cable lengths and determining cable rates. These tools from Fluke Networks, NETSCOUT, and SignalTEK ...
It’s based on Ookla’s Speedtest, though.