First, refrigerate it immediately
Whatever the parcel’s condition, get the vial into the fridge as soon as possible. Further temperature exposure only compounds whatever degradation may have already happened; stopping it is the first useful action regardless of what happens next.
Then assess what happened
Check the ice pack: is it still cold or fully melted at room temperature? Check the insulation: was it intact, or missing/damaged? Check the vial itself for any visible cloudiness, discoloration or particles. These together give a rough picture of how serious the lapse likely was.
Contact the supplier
A supplier with a genuine cold-chain process wants to know when it’s failed, both to make it right for that order and to catch a packaging or courier issue before it repeats. Documenting the parcel’s condition with photos before opening it further is useful evidence either way.
Weighing whether to use it
A vial that arrived cool with a partially frozen ice pack, just slightly delayed, is a different situation from one that arrived warm with a fully melted pack after a multi-day delay. The latter is a much stronger reason for caution, particularly for a reconstituted or otherwise more fragile product.
Preventing a repeat
If a specific route or season seems to correlate with cold-chain failures (a known slow delivery area, a heatwave), flagging that to the supplier, or choosing faster dispatch options where available, reduces the chance of it happening again.