I am not sure exactly what the issue is; it could be many different things.
I assume you used to have another phone before you got the new iPhone?
EDIT: From your other post, we now know that you replaced your old phone with the new iPhone.
Based on the information from your other post, your Carloop probably needs new WiFi credentials added to connect to your iPhone's hotspot.
EDIT: Now we know from your other post that your Carloop uses a Photon as its microprocessor.
I suggest heading on over to particle.io for more information on adding the iPhone WiFi credentials to your Photon.
There are several ways of doing this, so the method is your choice.
Make sure you do not wipe out the existing WiFi credentials used to log into your computer and tablet....
Do you still have access to your old cell phone? It could be that some custom .html or .php files were installed on your old phone. If that is the case (I am assuming), you will need to copy those files over to your new phone.
Are you able to login to particle.io on your new phone? I have no idea if this is needed for your use case or not, but it is one more thing to check while I am taking guesses.
EDIT: This last case is extremely remote; do not bother trying this until the other options are exhausted. One last possibility that I can think of at the moment, is that the firmware installed on the microprocessor of your Carloop has something specifically built-in to log in to your old phone. You may have to update the firmware and re-install. Do you still have the source code written for your Carloop?
Hope these ideas help.
PS. Create yourself a mini manual on each step as you sort this out. It may help you or another partner in the future!