Hi Sizer7534,
Thanks for reaching out in Apple Support Communities. I understand you're having trouble downloading Call of Duty: Mobile on two iPhone devices. I also see you've performed a reset and updated your devices, but the issue persists. I know it's important to be able to download the games you want on your devices; I'd like to help.
First, I'd suggest verifying that you have enough available storage on each device; Call of Duty: Mobile is 2.4GB in size. While reviewing the storage available, also check to see if Call of Duty: Mobile is listed as consuming any storage on your device and remove the data: How to check the storage on your iPhone, iPad, and iPod touch
After you've checked those things and if you make any changes, try using these steps next:
If you continue to have trouble, since this is only happening with Call of Duty: Mobile, I'd recommend reaching out to the app developer for additional assistance: How to contact an app developer
Best Regards.