1. Open App Store.
2. Click on something other that "Purchases".
3. Hold down the Option key, then click on Purchases.

That should again highlight Lion and allow you to (re)download it.

Is that what you seek?

Harv
27" i7 iMac (10.13.6), iPhone Xs Max (12.1)

Those who can make you believe absurdities can make you commit atrocities. ~Voltaire