UM-one MK2 doesn't work with Big Sur

That was curious! I just installed the OS update to 11.1 (with some trepidation!) and the MIDI Studio problem I mentioned above is resolved! I think a lot more bugs were fixed then in Apple's simplified notes.

I have a feeling Roland has created several issues for me. Regardless if they have fixed their driver to work with OS11, I suspect something is wrong in their install script. After upgrading to Big Sur and discovering the UM-One did not work, I read on Roland's web site that reinstalling the driver might solve the problem.

1) I tried this on my iMac and it crashed the Audio Engine in Finale. The fix for that was to use a feature in Finale to "Reset Rewire" which solved the problem.

2) I reinstalled the Roland midi interface driver on my MacBook Pro and it resulted in not being able to "Allow a third party driver to install" in System Preferences>Security & Privacy. The actual problem is that I cannot unlock the System Preferences. I spent over an hour on the phone with Apple Tech support and they are working on the problem. Apparently this is a recently discovered problem and Apple is still trying to figure out why it happens for some users. I think the Roland install is creating some security "kink" inside of the OS.

3) I installed the Roland UM-One driver for OS 10.13./10.14 on an older iMac running OS 10.13.6 in an effort to gain back my midi interface somewhere within my system. After installation, the iMac would not successfully complete the boot up! After several attempts and an unsuccessful "safe start" I reinstalled the OS. After an hour or so to reboot, it worked. And, the midi interface works! (So, obviously the driver installed.)

Seems to me Roland is messing with my computers!!!

This did NOT work for me. I have OS 11.0.1 installed and tried re-installing the Roland UM-one MK2 10.3 driver for Mac OS 10.15. No luck with the midi interface with the switch in either position on my iMac or my Macbook Pro. It does work on a machine with OS 10.13 (with the switch in COMP position) so I know the interface is working.

I tried running the Roland install helper app to no avail. It says the driver did not load and had me check Privacy and Security to see if the driver was blocked there - nope. Several restarts, no luck.

I assume you meant OS 10.15 not 10.5. The driver for 10.5 is a 32 bit version and will not install under Big Sur (OS 11.0). As noted above, I've already tried this without success. I am not successful getting the driver to load under Big Sur.

Glad to know I am not alone. Now all I need is the fix!