Motion 5 will not open

You have to tell us more.

What mac, OS version, Motion version?

What exactly happens when you try? If there is some error message, post a screenshot.

Whenever there is a problem with Motion or FCP, it’s worth deleting the application preferences. To delete preferences, hold down command and option while starting Motion and click Delete Preferences. If it then starts ok, adjust the preferences as you like them and it’s done.

If the problem persists Please run Etrecheck and post its full report here.

Use the “additional text” button and paste the report into the text box.

First of all, follow the advice from Luis.

I'll add that one of the common causes of Motion being very slow to open or not opening at all is from plugins becoming unresponsive after a Motion, FCP or macOS update. Often it is a plugin from Pixel Film Studios, but it could be any other plugin - but the point here is to remove all your PFS plugins first and see if that solved the problem. From there, remove them all 1 by 1 to isolate. With macOS 11, and the most recent Motion updates, many older plugins may include assets that no longer function. When you open Motion, the first thing Motion will do is load all the plugins you have installed, for Motion and for FCP - so if one of your plugins is not responding - this will prevent Motion from opening.

Try opening Motion by opening an exisiting motion project - does it open normally this way?