No. I said, "Connect on Join checkbox, in addition to Join on Connect".

The Edit Channel dialog has a Join on Connect checkbox. It needs a Connect on Join checkbox, which is selected by default.

If you select a channel from the Favorites menu when you're not connected, mIRC attempts to connect and join it. This is not always desired. If you remove the network from the Networks combobox, it returns to All Networks, instead of None, which is not always desired either, and in fact quite surprising to me, although No Networks would never perform the operation.

An option in the Options -> IRC -> Options dialog, Connect on Join may suffice.

"Connect on Select from Favorites" may be a better title for the operation.