Hi,
Some options in mdp files are changed from version 4.5 to version 2020.5 and some functions have changed.
Please have a look at
https://manual.gromacs.org/current/user-guide/mdp-options.html
The mdp file above mixes setting of energy minimization with molecular simulation. To perform energy minimization you can use as integrator (steep or cg or …but not md) in mdp file.
To have one step MD, the options
emtol = 10.0
emstep = 0.01
are not used.
I guess the aim is to simulate a DNA in a box of SPCE water, then one has to set parameters for the treatment of short and long range intergration in the mdp file. Please look at the mdp option documentation also for this.
Best regards
Alessandra