I'm writing this for anyone facing the same issue. I was facing the same thing with Maple 2022, where I was using a license server in an off-site location, connected through a VPN. 

The issue is that the license check only has a 0.1 second window of validation. If your connection is high-latency, it might fail the check before the server has actually replied. In order to fix this (For Windows clients only, as far as I've seen), create a system environment variable called "FLEXLM_TIMEOUT" with a value of 10000000 (this is 10 seconds expressed in microseconds).

Fixed it right away for me. Make sure your ports are actually open. It requires port 27000 as well as another one which you can set from the vendor file. See here for how to to force it to a specific port: https://faq.maplesoft.com/s/article/License-Server-Setup-Tips?language=en_US

Just in case the link goes down, you have to add the port in your server license file, such as:

SERVER asdf.domain.com fnih4ij2342 27000
VENDOR maplelmg PORT=27001