I’m using the same device, I stopped using signal about a year ago, my phone has updated versions a couple times since then, every couple months I would go back to find a password or login that I was texted, a couple days ago I started signal to look for a login and it said it had to update, now it says I have to “secure your number” and use it to log in to retrieve my messages.
Use a messenger that doesn’t require to to log in to view data stored on your phone. I’m sure the data is there, I’m just not allowed to see it.