VPN issues

I'm having the same issues with connecting to my wife's company's VPN.  I thought I'd be able to get away from Spectrum, but T-Mobile doesn't like like a viable solution - despite significant efforts on my part to make it work.

About three weeks ago, I tried connecting to T-Mobile. Initial attempts in connecting to T-Mobile weren't good - and I was only able to achieve download speeds of 15 mbps.  I called their technical support and found they were having tower/equipment issues - and had been for about 3 weeks - with no anticipated date for repair.  I put back the Spectrum service and told them I'd try it again when they had their equipment issues fixed.

ON 2/1, I re-installed the T-Mobile Gateway equipment - NOKIA 5G21 GATEWAY: T-MOBILE HOME INTERNET and connected T-Mobile Gateway via Cat 5 ethernet directly to my TP-Link Archer AX11000 wireless router.  I did repeated internet bandwidth testing using Speedtest - both through my computer's Chrome browser, and through the TP-link app - directly from the wireless router.   I wasn't having any issues with any of my internet-based usage and needs -   achieving download speed ranging on the low-end from 50 Mbps to 110 Mbps. We can stream 4K programming to our TV's, monitor outdoor 1080p security cameras, conduct video conferences, and all of the normal data applications and downloads. 

Using a Cisco AnyConnect VPN is a WHOLE DIFFERENT STORY.  It DOESN'T WORK with T-Mobile. As soon as I connect to the VPN, my internet speed/bandwdth is non-existent and I can't access any of the company systems.  Beginning on Friday, I spent two days troubleshooting the issue.  In every case, I would have connection bandwidth speeds between 50 Mbps to 110 Mbps on all of my devices - including the computer I need to connect to the VPN.  With my first attempt, I used Speedtest on two successive runs, with upload speeds were 15 and download speeds were 49 and 72.  Next, I successfully connected to the company VPN  (IPsec) IPv4) , ran Speedtest, and received 10 down and 1 up, and then 6 down and 10 up.  I simultaneously ran the TP-Link Speedtest app and received 86 down and 7 up.  I disconnected from the company VPN, and recorded speeds of 70 Mbps. 

Later on in the evening, we ran more comparative tests and the results were even more disconcerting.  The T-Mobile speeds in general were lower - averaging about 50 down and 8 up - as measured both on my wife's computer through her Chrome browser using Speedtest prior to VPN connection and independently on my TP app also using Speedtest.  However, once connected to the VPN, opening the Chrome browser and attempting to run Speedtest, I couldn't even get the Speedtest to run - receiving "Download Test Error". 

The company's IT Director took the computer home over the weekend to troubleshoot it in his home environment with Spectrum.  He had no problem connecting through the VPN, and recorded speeds in excess of 70Mbps.

This evening, I again attempted to connect to the VPN, and had the same results.  After a 2 hour wait to get T-Mobile support, I had a nice support rep who simply took down my information, created a trouble ticket, and said someone will get back to my in 24 - 48 hours.  After reading all of the other people who are having the same issues, and having no addressable solution, I placed an order for Spectrum to have my service restored.