Hi TDS,
Much like @PhilipDAth I recommend verifying if AVG is blocking the communication from the SM App. Disabling AVG would be a quick way of doing that. If it can be isolated to AVG blocking the traffic, you would need to follow up with AVG and see what recommendations they provide to allow communication. One common block is the firewall functionality of some antivirus solutions. If the communication is blocked due to firewall rules, you can check on your Meraki dashboard under Help -> Firewall Info for a list of needed IP subnets and ports used for System Manager communication.
If further assistance is required to narrow down the reason for failure, feel free to open a case with Meraki Support and they can have a look as well.