WowAce

What version of Grid2 are you using? Grid2 r916 (2019-08-29)

What game client version (windows or mac) and language are you using ? Win

What steps will reproduce the problem? ---

  
Did you try having Grid2 as the only enabled addon and everything else disabled? Yes

Was it working in a previous version? If yes, which was the last good one?  No

Do you have an error log of what happened? If you don't see any errors, make sure that error reporting is enabled (`/console scriptErrors 1`) or install [BugSack](https://mods.curse.com/addons/wow/BugSack). It's not a bug.

Playing as a priest, I impose Power Word: Fortitude on the members of the group and the add-on correctly removes the pointer to the missing buff.

However, if someone has already cast this spell by another priest, then Grid tells me that the buff is missing.

I tried all the options including the creation of an additional buff with the condition "not mine" and nothing helps. Shows a pass of either my buff or someone else's.
Can a simple buff check be made for such things?

Working fine here. I only know one condition that could trigger that behavior:

Maybe you are using the "Use SpellID" option on some status which tracks the same buff: If there is a status with the "Use SpellID" option checked, and another status (tracking the same buff)  with the "Use SpellID" option unchecked (tracked by buff name), one of the status is not detected.

This include Groups Buffs, maybe  "Power Word: Fortitude" buff name (or his spellID number)  was added to the list of some group of buffs status.

No, I enter the name of the spell manually both times without using an ID.

Would it not be difficult for you to show a screenshot of all the relevant settings for this buff?

There is nothing special to configure about the buff, only click the  "show if missing" option.

Export your profile to text format (profiles/advanced) and send my the data, you can post the info here or sendme a private message.