Agreed I would make a small weak starter and see if you get any growth. If it is totally frozen, all the yeast may be dead. But the only way to be sure is to try a starter.
You may need to take gravity samples to determine if any fermentation takes place. I have had some show little to no visible signs but did propagate.
If there is any action in the small starter then you can step up to a proper sized starter.
I, for sure would give it a try before just tossing it and buying new yeast.