Just got Sibelius and it is freezing on startup.

1. This is a Logic forum, not a Sibelius forum
2. Explain how it has something to do with Logic.
3. You may need to go to https://www.sibelius.com/cgi-bin/helpcenter/chat/chat.pl?com=show&groupid=3&guest=1
4. Always provide information of your set-up: MacOS, Computer Model, Software version
5. Sibelius runs fine here on MacOS 15.3.2, M2 MBP, Sibelius 2025.3 (silicon)
6. I've never heard of something like renaming the system (plugin) folder, unless you want the folder NOT to be recognized by the system and applications including Logic, Sibelius and others.
7. Your issue indicates that you may have incompatible plugins installed on your computer.

The reason why AVID gave you the tip to rename the plugin folder can only lie in finding the cause and, in this case, proving that the problem lies with the plugins. This can be one or more old, incompatible or corrupt plugins.

However, I would never rename the system plugin folder, rather remove the plugins from this folder one by one (and move them into a folder on another location e.g. Desktop) to find the culprit, which is a process that can be very labor intensive. To speed up the process, I would remove several plugins at the same time and check that Sibelius can now be started.

Before doing this, you can look in Applications > Utilities > Console > Crash Reports to find a hint, what is causing your issue.