GL-MT300-V2-11D tethering / repeater to iPhone

I want to connect a piece of hardware with dhcp cat5 port to the internet on its own connection. Therefore gl-mt300 connecting either with 3g/4g modem or tethered to phone or repeater to phone.
I have started with tethering to phones. In particular iphone 6s and iphone5s.
I set up Personal Hotspot. I attach with usb cable. I get do you trust on the phone I say yes. That is all I get. I then try connecting to the published hotspot wifi and get wrong key (I have even simplified the key). I can connect via the iphone using a laptop without a problem. I can also connect the gl-mt300 to my standard wifi (ADSL) router.
Are there any tricks to getting this to work?
I am willing to pop out and get a usb dongle - I have tried an out-of-date one which is immediately recognised as a tethered device. Is this the way to go?
Thanks and apologies if this is covered somewhere, if so please point me there. Thanks, Peter

OK so I found another post with a similar topic. I updated firmware to approved gl-mt300n-v2-3.012 (Japanese). Have downloaded gl-mt300n-v2-3.013-0131 which if equivalent to the gl-mt300n-3.013-0129 may fix some of the iPhone connectivity issues. But then followed advice toggling Personal hotspot off and on on iPhone this seems to get it to be picked up by the gl-mt300n-v2. Seems to be working but something is not quite right.

Yup, it is an exist issue on MTK chip. You must turn it off and turn it on again to let it work.