Someone can be timing out for many reasons.
Trying other game betas might help (x86-64 chromium, Dev branch, and Pre-release branch)
Clearing download cache
Verifying integrity of files
GMOD/Steam re-install
reduce the number of mods downloaded!
locate the cl.db file located in the Garry's Mod folder and then delete it. Then load into the server. (This has been a fix so far)
In some cases, a PC reset might be needed (This should only be decided as a last resort).
How to verify files?
https://help.steampowered.com/en/faqs/view/0C48-FCBD-DA71-93EB
How to clear download cache?
https://help.steampowered.com/en/faqs/view/6AD7-820D-8BE5-E51F
Connection failed after 6 retries.
Try changing the client port. First Go into Garry's Mod properties in Steam > Then go to Set Launch Options > put in +clientport 27006 OR 27005 and then doing the same thing into console to 100% make sure the client port is working.
Try flushing DNS cache. You can do this by opening CMD and then pasting the command ipconfig /flushdns and then disabling and enabling WiFi.
Try changing the DNS servers being used. The most common one someone can use is 8.8.8.8 and 8.8.4.4 (Google DNS).
How to change DNS server?
Press the Windows key on your keyboard.
Type in “control panel” and open the Control Panel app.
Click Network and Internet.
Go to Network and Sharing Center.
Click on Change Adapter options.
Right-click on Ethernet network and click Properties.
In the Ethernet Properties window, click Internet Protocol Version 4 (TCP/IPv4), then select Properties.
In the Internet Protocol Version 4 (TCP/IPv4) window, select Use the following DNS server addresses:
For your preferred DNS server, type in: 8.8.8.8.
For your Alternate DNS server, type in: 8.8.4.4.
Make sure to enable Validate settings upon exit box, then click OK.
Stuck on LUA Started is a common issue when joining a server, here's a list of fixes that may help!
Most of the time waiting for GMOD to load can fix this issue (let it load, do not tab in and out).
Reduce the number of mods downloaded.
Clear download cache & verify integrity of files.
Change to a different Beta (x86-64 chromium + 64-bit binaries, Dev branch, and Pre-release branch).
How to verify files?
https://help.steampowered.com/en/faqs/view/0C48-FCBD-DA71-93EB
How to clear download cache?
https://help.steampowered.com/en/faqs/view/6AD7-820D-8BE5-E51F
sad to see you go Bon, you've been a great guy to talk to and have been the best Head of Support! Like beckett said you've exceeded the highest of expectations!