Error found - cell type [xyz] not supported
Full message text
Error found in [XYZ] -- Cell of type [XYZ] not supported
Case 1 - Weirdness of cell format or cell data
This one is pretty straightforward to resolve usually. The parser will tell you right where the offending cell is (in 95% of cases) and you'll just want to remove it, correct its format or pattern, or remove any weird / special characters.