Requests for technical support from the VASP group should be posted in the VASP-forum.
As a minimal setup, VASP requires the following input files: the INCAR file, the POSCAR file, and the POTCAR file. However, there are more optional input files, e.g., the KPOINTS file, the KPOINTS_OPT file, the ICONST file, etc. A complete list is provided below.
VASP calculation are often continued on top of a previous VASP calculation. So, in case a calculation is restated, the output files of the previous calculation can be input files for the next calculation. For instance, the CHGCAR file, the WAVECAR file, the CONTCAR file copied to POSCAR, the ML_ABN file copied to ML_AB, etc.
Finally, there is a special input file to induce a soft stop of the calculation: the STOPCAR file. It is not used in a standard workflow, but it might be convenient to stop a calculation manually when it takes too long or a technical issue on the compute engine arises.