Since ledger has revamped all of their nano s applications (to save space so that more apps can be installed on the nano s), i guess that you were trying to use/install a fork of BTC.
In this case it makes sense that you need the BTC app to be installed (since any forked coins use the same libary included into the BTC application).
The same probably also applies to ETH, especially when trying to use a fork (not sure if there is any supported by the nano s at all).
At least you have fixed the problem, that's the most important thing