The external Flash is not showing up in the configuration Menu when using Pixel TF-321 hot shoe. Is this the wrong adapter for that camera, as there is no X connection? I want to trigger a studio flash via sync connection. Can you recommend me a working hot shoe? Thanks!
Unfortunately, your canon EOS 4000D is a very stripped down entry level camera.
Looking at your photo of the hotshoe, I now realize that Canon has removed or eliminated the center hotshoe contact. This is the contact you need to make the sync connection with your Pixel TF-321.
The 4000D will only work with Canon brand ETTL flash units.
There is no way that I can think of to make your camera sync with an external studio flash.
Any other Canon camera would have had this contact. I find this very troubling and I can't really see how this can be seen as a cost saving measure.
EDIT: There are just 2 Canon cameras affected so far. They go by various names depending on where they are sold: 1500D/2000D/Rebel T7/Kiss X90 and 3000D/4000D/Rebel T100
There is a solution - Godox XPRO-C. 70 bucks and I'm able to use the sync! Works with 2000D and 4000D!
Apparently Canon has removed the ability to manually trigger a non E-TTL flash with the 4000D by removing the center pin of the camera's hot shoe.¹
This is supposed to be locked in a photo booth.
If you are bound and determined to use the EOS 4000D, with it's non-ISO compliant crippled hot shoe (SHAME, SHAME, SHAME, on you, Canon!), then you might try reflecting the output from the camera's built-in flash to the optical sensor in the strobe with the strobe set to 'Photosensor' triggering mode. Set the camera's built-in flash to manual flash power. Turn off red-eye reduction plus anything else that causes a 'pre-flash'. Since the camera is mounted inside your photo booth, it should be fairly easy to block the camera's flash from directly illuminating the posing area while bouncing the light from it inside the 'behind the wall' area to trigger the strobe.
¹ Which, in this case, should probably be called the 'somewhat lukewarm shoe'.
I have Canon 2000D and learned the hard way that my camera is crippled. Thankfully Godox X1T-C with firmware upgrade v26 bypasses the issue with lack of central pin. So if you want to add remote flash trigger in your toolbox than get Godox XPro or X1T-C trigger. Just be aware that Godox XPro and X1T-C are compatible only with Godox X system. To trigger my Neewer speedlites I had to get Godox X1R-C as well. One was enough as I'm setting my other speedlites on optical trigger. So being able to wirelessly trigger one speedlite works good enough for me.
Bought Godox X1T-C and it worked very well for my Canon 3000d. Don't forget to update to latest firmware released 5 May, 2019.