1 of my 3 PCs will not connect to my softether vpn

On my home network I setup a Softether VPN server (L2Tp/IPsec with Pre-shared Key) on a Raspberry Pi4. Using an older Dell Windows 10 Laptop (using windows built-in vpn client) I can connect and access my LAN locally and remotely (using an iPhone for my hotspot).

I have another local PC running Win 11 Pro on my lan and have setup the windows vpn client and can login although I have not tried this remotely.

So I assume this is not a server side issue? However using a newer Dell Win 11 Pro laptop I cannot connect and I get the message that there is a security issue preventing the connection.

The Dell Win 11 laptop has the latest Windows updates and I've seen the issue that a recent Windows update (April 2024) has caused Win 11 VPN connections to fail due to a TPM certificate issue. I wanted to uninstall that update but I do not seem to have an option to do that in the "Uninstall Updates" under Windows Updates. I did see that an Update posted on Verge states - "May 14th: Microsoft now says the issue should be resolved after installing the KB5037771 update." I have confirmed that this update was installed on my Win 11 laptop. My win 11 pro Dell laptop has version 23H2 with OS build 22635.3785. I am using the windows built-in VPN client (L2Tp/IPsec with Pre-shared Key) on all 3 machines. I have tried some common recommended remedies such as:

-uninstalling / reinstalling all WAN drivers in device manager

-Flushing DNS

-turning off the firewall

• turning off IP V6 on the SE network adapter

-unchecked Use default gateway on the remote network option on the SE network adapter

-adding a registry edit to allow an exception for UDP

• edited and set registry AssumeUDPEncapsulationContextOnSendRule value to 2.
• verified Proxy settings are off

I do not want to reinstall Windows.  Any help is appreciated.