ccgrg origially written for Mathematica 8 work properly with higher versions up to 11.1.
To run the package in higher versions of Mathematica you nead to restore the previous functionality of functions Solve and ValueQ. To do that please put in your notebook the following two lines:
If[$VersionNumber >= 12.2, SetOptions[ValueQ, Method -> "Legacy"]];
If[$VersionNumber >= 12.2, SetOptions[Solve, Assumptions -> {}]];
just after loading ccgrg.m.
