Wäre möglich wenn die Züge fahren würden. Aktuell kein Grenzüberschreitender Zugverkehr Schweden - Norwegen 

Yes, it’s just like @seewulf describes, Norway does not allow any cross-border trains since the start of the pandemic. This is very disappointing but it does not look like there will be any changes in the near future. You can check Flixbus and Bus4you to go to Oslo but you need to pay extra for them.