Hi Matthew, welcome to the MFiX forum.
Please post your files here if you want help.
If you load an older file into a current version of MFiX, the GUI will attempt to convert your file - certain keywords have been removed or renamed, etc, and the GUI does its best to migrate these to the current settings. Also CGS units are no longer supported, the GUI will convert CGS cases to SI.
However the GUI may not catch all obsolete/deprecated keys, especially for 20 year old input files. But when you run the simulation, the solver will complain about unknown/deprecated keys, and you will get a popup from the GUI allowing you to edit or delete the offending line. It’s a bit of an iterative process but with a bit of patience you should be able to get your case to run.
For reference you might want to look at the file deprecated.f in the MFiX source directory.
– Charles