Node is latest version, fully synced, pruned.
It just get's weirder: in bitcoin-qt -testnet it shows available balance of 0.01 tBTC, but in Send > Inputs, there is nothing, quantity = 0, amount = 0.
Do you try it with the mainnet, not testnet? Balance on test net has no real-world value so I think it is likely a possible reason.
Definition
A global testing environment in which developers can obtain and spend satoshis that have no real-world value on a network that is very similar to the Bitcoin mainnet.