Connectivity to Luma cameras for iPhone12 using Luma app

I recently purchased an iPhone12, and it's been working great. Last week I had Luma Surveillance cameras installed with the Luma app for iPhone. No issues accessing live view with my iPhone while in my home with WiFi, but unable to access when out and about town with cellular or open wifi. I have a vpn, but shut it down as well as all open apps with no improvement. The installer has contacted Luma, and there has been no successful suggestion other than perhaps the issue is with the new iPhone. I opened a discussion in the integrator system's (Control4) forum, and there was a suggestion that iCloud is the issue. If that is the case, then why am I able to get connectivity at home? I'm suspecting the problem is with the Luma app for iPhone. Any ideas? Thanks.