I set up my wife into family sharing with me so we could both use iCloud and share the monthly allowance. Each time I invite her via text message the message will not go through

Hey there Browser314,

We'd like to help rule out some possible causes, along with learning more to see how we can help:

1. If we're correct in understanding that you've set up Family Sharing successfully, and each of you have your own Apple ID separate signed in, are these the steps you're taking to try sharing your iCloud+ subscription? Check out: Share iCloud+ with your family It also lists the requirements for each device.
2. We see you're using an iPhone 8 with iOS 13, but the latest version for your model is iOS 16.4.1. In case you needed it, this link shows how to first back up, then Update your iPhone or iPad. We also recommend making sure your wife's device also has the latest compatible version.
3. If both devices are already up to date, have you already tried a restart of both since this started to occur? If not, here's a link that shows how to restart an iPhone: Restart your iPhone

Cheers!