Opening Glyphs 2 file in Glyphs 3

I wanted to switch from G2 to G3. While every glyphs is compatible in my G2 file, when I open it in G3 it gives me this red sign that it’s not.
If I open one of the glyphs it is showing me the proper inter/extrapolation but the red sign of “notcompatible” is on anyway. What might be the issue?

The default mode for checking compatibly has changed. If you have three masters and only two are interpolating, Glyphs 2 would not complain about the third not being compatible. You can switch back to this behaviors by adding a “Enforce Compatibility Check” custom parameter to the font settings and uncheck it.