What would be potential causing for this account not being visible even though it's active with the correct subsidiary?

Not being visible where exactly?

When selecting an account (i.e. on inventory adjustment or journal entry), the 1155 account doesn't appear.

My guess would be the account has a currency specified and the currency on the transaction doesn't match. Could also be you're looking at a location/department restriction by user relevant to the account setup and the transaction.

It seems like this issue is related to the currency. What are some possible solutions? The accounts shown don't have a currency type under their setup.

Assuming that the account has existing transactions you can't do anything as you can't change the currency once the account has transactions. An account without a set currency can be used for any currency transaction, what you have is a common problem through poor understanding of the setup.

Thank you for your assistance, Simon. I was able to create a new account without a currency solving this issue.

np