We have heard reports that some players are not able to play crossplay, and there's an important setting to review on your hardware!
Players on Xbox must allow Crossplay with a setting that is found under Privacy and Online Safety.
You can access this very fast by going to https://www.xbox.com/en-US/user/settings/privacy-and-safety, making sure you log in, and switching to the Xbox and Windows 10 devices Online Safety tab, and ensure that "Allow" is checked! Then scroll ALL THE WAY TO THE BOTTOM to make sure you Submit!
It is also possible to find the same settings on your Xbox by going to settings:
Settings> General > Online safety & Family > Privacy & Online safety > Xbox privacy > Account Privacy & online safety > “You can join cross-network play” > Allow / Block. Then back all the way out with the B button, then force close the game you were playing or reboot the Xbox fully to make sure settings take effect properly!