Indicates that there is an issue with the sketch.
Probably a lost projected reference.
If you Edit the 3D sketch - you will probably find some pink geometry somewhere (another indication of an issue).
Attach the file here and end all doubt.
That is an Informational Error.
Windows 10 x64 -16GB Ram
Intel i7-6700 @ 3.41ghz
nVidia GTS 250 - 1 GB
Inventor Pro 2018
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