I can’t open my Mac Pro 2018. I have followed the command R procedure but I continually receive either an explanation mark or a question mark

It may be possible that your recovery partition on your Mac Pro is corrupted and you will have to use Internet Recovery instead.

See if the following article can help: About macOS Recovery on Intel-based Mac computers - Apple Support

Did you review the link I provided you? You would power up your Mac, and then, immediately hold down the Option-Command-R keys.

What happened prior to this issue that it is happening now? Did you try updating, or deleting system files, or something else?

Sorry, I wasn't trying to be rude. Just wanted to be sure that you followed the correct steps. It appears that you have.

Unfortunately, based on your comments, you may have purchased a "broken" notebook. At this point, I would suggest that you return it for a full refund.