What does 'No carrier ' mean on Play Store?

It means that Google cannot retrieve the carrier info on your device. Some possible causes:

1. The SIM card is not inserted, or inserted incorrectly/broken (can't use telephony feature)


2. The SIM card is inserted correctly, but Google cannot identify it (e.g. an issue with Republic Wireless)


3. The device doesn't have SIM card slot (e.g. tablet)

As far as I know, the text "No carrier" is only an informational text to identify which device you are choosing, and it's not an error message. I have installed some apps to my older phone without carrier, without any problems.

Regarding app installation, it may/may not affect the installation. Some apps are restricted to certain carriers (usually carrier's apps themselves).

For your specific case, since you've mentioned on other post that other device with same carrier could install Cardboard, but your device didn't, it means that the carrier is not the problem.

On the other hand, based on GSM Arena, Samsung Galaxy J7 doesn't have gyroscope, which is required for Cardboard.