Devices that previously connected to wifi, now refuse to connect, help?

I'm trying to connect my devices to my wifi, one device (kindle fire) was previously working and connected and after a while I noticed my other devices (both mobile devices) would refuse to connect. I linked my kindle up with the wifi probably about a year or so ago, the password has not changed since. I was thinking maybe it was just the mobile devices that had a problem, i then tried connecting them to my sister's wifi nextdoor and they worked just fine. I wanted to see if it would do the same to my kindle so on that, i went to connections and chose "forget network" on my wifi. I then went to type in my password and reconnect and it attempted to connect then showed up as "unauthorized" or "unavailable" or something like that.
my mobile devices do somewhat the same when i try forgetting the network and reconnecting, they attempt to connect then fail and keep doing so until i choose "forget network" again.

this is quite frustrating, anyone else had this problem?

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