Basically and briefly,
Normalisation = transforming a data set to conform to a normal distribution. Converting to a frequency is NEVER a normalised transformation
Standardisation = ensuring each point of the data set is comparable to the others, either directly or relatively depending on the calculation
The information you have received is incorrect, ...
Answer from @user1271772, converted from comment:
Try on this site: https://mattermodeling.stackexchange.com/questions/tagged/gromacs. There's an entire GROMACS tag there.
Answer from @vishal-kumar-sahu, converted from comment:
Try running/resuming using -cpi the simulation again, I got NaN error and rerun kept continued.