Hi All! Do all Sonic Charge plugins support macOS Tahoe yet? Thanks!

Yes

Does that include Synplant 1? Although I reinstalled it twice, sadly Logic Pro 12 won't even see it.

Yes, Synplant 1 works on macOS Tahoe here, including in Logic, so this does not appear to be a general Tahoe or Logic Pro 12 compatibility issue.

Since reinstalling did not help, the next step is to try a Full Audio Unit Reset in Logic's Plug-in Manager. If Synplant still does not appear after that, please let us know which version of the Synplant 1 installer you used.

Please note that Synplant 1 is a legacy product and is no longer officially supported.

Thank you for your quick reply Magnus,
Of course, I'm fully aware that version 1 is legacy. I found it weird because this is a new Mac on which I've just installed both Synthplant 1.2.2 and the latest Microtonic version and the auto authentication worked and confirmed perfectly. AU reset didn't seem to change anything. But today I'm very embarrassed to say that all it needed was a restart of the Mac Studio. I usually leave my workstation to sleep, but since I came across another unrelated issue, I had to restart today, and what do you know, there it was! Truly sorry about that.