Use your preferred text editor to open the test log file. For example,
gedit /home/user/deeps/gmx_MMPBSA_test/examples/Protein_ligand/ST/3.log. Check the error output. Also, check the gmx_MMPBSA.log file in the same folder (for example,
gedit /home/user/deeps/gmx_MMPBSA_test/examples/Protein_ligand/ST/gmx_MMPBSA.log) to get the exact error output