RDP over SonicWall SSLVPN suddenly stopped working. Running out of ideas and options.

My wife and I own a business and we've been using a SonicWall SSLVPN connection to remote from home into our office network. From there we RDP using local (local to the office network) IPs into our office desktops.

This has worked flawlessly for the past couple years, and we've been working from home exclusively since Covid.

We share an office space with my father in laws company and last week he completely unannounced reset the SonicWall router. My wife was connected at the time. This has happened before, and simply reconnecting worked fine. This time, it's giving me a couple error messages:

The first time you try it it's saying:

Internal error has occurred

Then when you try it again within a few minutes it's saying:

Remote Desktop can't connect to the remote computer for one of these reasons:

1) Remote access to the server is not enabled 2) The remote computer is turned off 3) The remote computer is not available on the network

I asked my father in law why he rebooted the router and he said "it was running slow". Apparently rebooting it solved whatever problems he was having.

The other thing is, our domain we use for our AD was set to auto renew but for some reason didn't. My wife and I actually looked at it that morning and it said "auto-renew" but when my wife checked it later it said "paused" or something similar, she couldn't remember exactly and she just paid it immediately. I'm not convinced that has anything to do with it, because I don't think it ever actually got shut off.

At this point I've tried everything I can think of.

The VPN seems to be working fine.

I first tried rdping to different clients at the office and none work.

I tried pinging the client and it will receive 1 packet and then drop all others. Pinging again causes all packets to be lost, but if you wait a few minutes and ping again, it will receive the first packet and then drop all others again. This leads me to believe access is getting denied somewhere. This is also similar to how I'm getting two different RDP errors.

Using RDP while at the office works fine, from one desktop to another.

I tried using different VPN and AD accounts, none allow the RDP connection.

I've tried connection from a different location other than our home. Doesn't work.

I've gone into the office to check settings on the office desktops computers that are being rdped into, I've checked the settings on the server (Windows 2012 R2), and I've checked the settings on the SonicWall. Nothing seems out of the ordinary. I'm not an expert by any means, but I just checked the settings I had to tweak initially to get RDP working.

I've tried removing and re-adding the host desktops at work to the domain. Did nothing.

I've tried tweaking the auth settings on the client and hosts. Nothing.

I'm completely out of ideas at this point and I'm hoping someone can give me some ideas on things to check or changes to make to fix this.