I have 2 Fire HD 8 tablets. One is a 2017 model, one is a 2018 model. 2018 model is using latest FireOS 6, 2017 model is on latest FireOS 5 version. I have 2 iphones, both running iOS 13.1.1. 2 different cell carriers. Turning personal hotspot on the phones allows the FireOS 6 model to connection fine, but the FireOS 5 model cannot connect. Have tried all the usual troubleshooting things (forget network, toggle wifi on and off, reboot device). The FireOS 5 device cannot connect to personal hotspot served up from iOS 13, but the FireOS 6 device can. Normal wifi works fine so doesn't seem to be a wifi problem. Is this an apple issue or an amazon issue?