Unable to setup SkyConnect

I am using the latest version (2023.4.4) of HA.

I ordered and received the SkyConnect a while ago and was able to configure and connect devices, like Philips Hue devices to it. Because I was limited in the usage (I was not able to use the dimmer switches anymore), I removed these devices from SkyConnect.
Last week I discovered that ZHA was in an error. I removed ZHA and all related integrations, and did a restart of HA.
After the restart, I got a notification, that a new device (SkyConnect) is found. But now it always fails to configure this device. I get all kind of errors like: ‘unable to connect’, etc.
Any suggestions?

I think I solved it:

I needed to install the Silicon Labs Multiprotocol addon first and then configure SkyConnect. I did not find that in the documentation!

Thanks, Xorfor. You made my day. I replaced hardware, reinstalled HA, rolled down backups, replaced cables, nothing helped and then I read your solution. Works like a charm. Cheers!