Sorry for the late reply…you’re probably on your 5th keg by now…
Hopefully you figured out the hardware issue. Sounds like they put a generic connector on the end of the hose. It also depends on the type of tap coupler you intend to use and there are many different kinds.
For most US beer, use the US Sankey type, see: https://www.barplan.com/draft_beer/index.html for more info.
I also recommend placing the CO2 tank OUTSIDE the keg box.
This allows for quick access to the pressure settings and keep you from constantly opening the keg box door to check pressure.
The CO2 is compressed, so as it expands it gets VERY cold (like a CO2 fire extinguisher) so there is no point in cooling your CO2 tank. 😆
See: https://www.barplan.com/members/page/kegkooler.htm
for more info in building your keg box.
(sorry that page is not all that easy to find, I’ll add more links, see sitemap in the membership site… https://www.barplan.com/members/page/sitemap.htm )