5511 and WD19TBS do not connect

I have had this 5511 for years and finally bought a dock for it after painstaking research to find one that was sure to work. According to Dell's dock PDF chart, the WD19TBS is compatible. However, once receiving it I have not been able to get it work. It will power the laptop, but that is all. No USB, no monitors. It will occasionally connect/disconnect several times (USB stick folder pops up, but no monitors) and then eventually completely disconnects. 

Laptop is up to date with all Dell drivers via Command Update and SupportAssist. Have tried the following:
-Installed Thunderbolt controller driver
-Installed Display link dock driver
-Tried to install Thunderbolt firmware update, but it always says that Thunderbolt Controller driver must be installed first (which it is)
-Tried to install Dell Dock Firmware but it says no dock detected

-Have tried to allow in Thunderbolt Control Center, but it never shows up
-Have adjusted all thunderbolt security settings in Bios, none seem to help

I may have left some things out and I continue to work on it. Why is this not plug and play?