[NAME]  Thunderbolt wouldn't be a factor here unless the display itself supports actual Thunderbolt rather than regular USB-C.  But it sounds like you've done everything correctly here.  The Latitude 5500 definitely supports video output and charging over USB-C, and you've got a suitable cable for that purpose, and you've confirmed other systems operate properly.  In terms of the underlying cause, if you have any other USB-C display to test with, that might be useful to determine whether this might be an actual hardware issue or else an interoperability issue with your specific combination of equipment.  Those do occur, unfortunately.  Dell has some early USB-C laptops that don't work with any of Dell's own USB-C displays even though they work fine with many third-party USB-C displays and Dell's own USB-C docking stations.  The only other thing I can suggest would be seeing if there's a firmware update for your display.  I found for example that my Lenovo USB-C dock didn't work properly with my iPad Pro when I connected it out of curiosity, but it did after I updated the dock's firmware.  If that doesn't fix it either, then this could either be a hardware issue (if you can test that with another display) or possibly a case of a problem that hasn't been fixed in current firmware yet.
HelloI recently invested in a new external monitor for my laptop. This monitor is a a 4k Samsung monitor with USB-C PD support, which I wanted to connect to my laptop using a USB-C cable to both power the pc and use the monitor for output.    The monitor is a Samsung S32AM70 which should support USB-C connection with PD according to specs. I have bought a separate cable with support for up to 100 W PD charging and a transfer speed of 20 Gbps. The laptop I have is a Latitude 5500.I have updated all drivers and the bios using Dell Command Update and have upgraded from windows 10 to 11 to see if this could fix the problem. I have run a full diagnostic using the Dell Support Assistant which gave me no errors. I have checked BIOS to check if thunderbolt was on, which it seems to be. I have checked the monitor and cable with two other computers. The first was a MacBook and the other was a PC from HP. Both of these work fine with the monitor and cable. When the monitor is plugged into the USB-C port, it seems to get an intermittent connection lasting about a second. This occurs every 2 or 3 seconds. This is not enough to get a picture, but you can see the USB-C source show up in the menu on the monitor. I have also observed another of Dells support programs complain about the power amount coming from the wire being to low wattage to effectively charge the laptop. This only occurred once though. The laptop does not charge using the monitor.Anyone who can sport something obvious that I have missed or is this a hardware problem with my machine? 
Problems connecting USB-C Monitor