Greetings nosbigtrebor,
Have you already performed a restart of your iPhone? If not, do that now: Restart your iPhone - Apple Support. Does this help to resolve the issue? Often this simple step will refresh the apps and software on the device to solve numerous problems you may encounter.
Does the issue happen when you're on Wi-Fi, cellular data, or both? Keep in mind, that if you do not have a cellular data connection available and you're only using Wi-Fi to send, you'll need to have Wi-Fi Calling enabled. Here's information to help: Make a call with Wi-Fi Calling - Apple Support.
Do you notice if the issue is present only when trying to send contacts with a specific carrier? If so, it may be an issue related to your carrier sending to the other. You would want to reach out to the carrier directly to find out more.
Does your iPhone show that you have enough available space to send and receive messages? You can check your available space by going to Settings > General > iPhone Storage, and verify that you have available free space on your device.