Build the Pi Computer, but Can't Access Umbrel

I’m trying to build my own node/server.
I bought all the pieces and built as per the directions. But when I go to http://umbrel.local/, it does not bring up Umbrel. At first it told me the device was not connected. Now I only get this message:

This site can’t be reached

Check if there is a typo in umbrel.local.

Also, Angry IP does not open on my MacBook Air, even with security permissions.

Thanks for any help. I’m a non-technie, so please non-technical language.