P2219H, Surface Pro 7, dock, not seeing monitors

@JKT  It's difficult to answer this question given that you didn't specify exactly what type of cable you're using to connect the displays to the dock, and which port that cable is connected to on the dock and which port it's connected to on the displays.  If you don't know what those ports are called, consider looking at the documentation for the dock and display (the latter available on support.dell.com) to find the names of the ports.  Or you might even find the information you need to make it work properly there.

@JKT  Ok, I've attempted to fill in some of the blanks here.  First, I'm assuming that you have a Surface Dock 2, like this one, and not an original Surface Dock?  Is that correct?  Do the ports shown on the back of the dock on that page match what you have?  If so, then when I checked the page for the P2219H to see what inputs it has and what cables it includes, the only cable included with the display that you would have been able to connect straight from the display to that dock would be the USB 3.0 cable.  But that does NOT carry video.  The USB 3.0 cable allows you to use the USB ports built into the display for things you want to connect to your system.  For video, the Surface Dock 2 only provides USB-C ports, but the P2219H doesn't have a USB-C input.  So you would need to buy a USB-C to DisplayPort cable, or you could get a USB-C to DisplayPort adapter dongle and then use the DisplayPort cable that was also included with your display, whichever is cheaper.  Obviously you'd need one for each display.

Hopefully I'm right about the dock that you have and what you've done thus far and therefore that this was helpful.  But a bit of general advice for the future, when asking for technical assistance, it helps to provide basic technical information so that the people here who are willing to help have something to work with rather than having to spend time trying to fill in a bunch of blanks on their own (or choosing not to take that time and thus not being helpful to you).  Just saying, "I have a Surface Pro 7 with an unspecified dock model, and a P2219H, and I connected some sort of cable between them, and it's not working," isn't all that useful.

Thank you so much for your prompt response. 

You are right.  the dock you have linked is the one I have (apologies I didn't even think to attach it as I thought there is no other).  Now if I buy the USB-C to DisplayPort cable you have recommended can I use it to connect 2 monitors as I am looking to have 2 external monitors plus my surface pro 7 as a third screen.

Thank you once again.

@JKT  Glad I was able to help.  You'd need to buy a USB-C to DisplayPort cable for each display, not just one, because your displays do not support being set up in a daisy chain.  They would both have to be connected directly to the dock, and therefore you'll need two such cables.  But yes, once you get those cables, you'll be able to run both of those displays and your built-in display all simultaneously, and independently (Extend mode) if you wish.