Using isolate in an assembly I can work on a few parts but when I exit the balance of the parts do not reappear.
Before you use isolate make sure all parts are shown. RMC in the top of the "feature manager design tree" where the name of the assembly appear and select show with dependents.
Now try it again.
I did find that selecting show with dependents made the parts reappear but even with all parts shown before using isolate I still on occasions had teh same issue of items not showing on exit isolate
Are you using an approved graphics card & driver?
Run the SOLIDWORKS Rx > Diagnostics to check
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