Real Sociedad are expecting Alexander Isak to stay until the end of the season, and they won’t let him go for less than his release clause.

Arsenal fans have been kicking off about the potential signing of Alexander Isak in the last 24 hours, after he was spotted in London on Saturday.
But the striker wasn’t at London Colney. He was caught on camera in a Selfridges with Real Sociedad teammate Adnan Januzaj, both seemingly just on holiday in England.
Isak responds after Arsenal decide not to activate his release clause
Mundo Deportivo report in their print edition (via Arsenic) that Real Sociedad are calm ahead of the final 48 hours of the January transfer window.
They plan to refer Arsenal to Isak’s full €90m release clause in case of any late bid from the Gunners.
As things stand, there has been no such approach. Isak’s agents haven’t received an offer, and Real Sociedad are expecting the player to stay.

We know that Arsenal like Isak. There are reports from plenty of sources confirming that information, and he’s consistently listed as one of the club’s long-term targets up front.
The Athletic are one of those sources, but they were pretty clear that Arsenal would try to negotiate a lower price if they made a move to sign the striker.
If Real Sociedad aren’t open to negotiations, then that kills the deal at source.