Retain INDEX MATCH Data From External File?

I've 1 master file with event info (dates, times, categories, prices etc). I have another file to track sales which uses index match to pull data from the master file (stored on a server) instead of double entering.

Upon opening the sales file, all the index match cells are blank until opening the master file, even after saving.

Is there a way to make the file retain all the data it pulls without setting manual calculation (manual spreads like a virus to other user's files - finance manager almost killed me last time)

I currently have a macro button set up to open/close the master file, but if I try to filter/sort the data without the master file open it all disappears again.