Trying to update Iphone 6 but continue to to get error stating that phone can not be updated because "activation can not be verified"

Just trying to use an older phone around the house as an ipod for connections to back yard and garage Bluetooth stereo systems. I have an iPhone 6 that sat in a drawer for the last few years. After charging it, its stuck in the set up pages. If I try either manual set up or to sync it with my current phone, right after the wifi login message pops up that its "Unable to Activate" and that "an update is required to activate your phone". I have already tried the restore it and that messages states "iPhone could not be activated because the activation information could not be obtained from the device". Not sure how to fix this but I'm just chasing my tail in circles!

any help would be appreciated