Clients showing outdated definitions but I tried updating content

Problem: I have 20-30 clients showing older definitions (beyond a couple days or more) and when I try to run a manual Update Content command, after 15-30 minutes I go back to check on the SEPM, the clients still show older virus definitions and not having updated.

Questions:

• What is a good strategy for updating these clients content and forcing them if they don't update?
• If they don't update, what is the best troubleshooting tool you all use to remediate handful of clients?
• How often do definitions download? I presume based on this document 3 times a day https://support.symantec.com/en_US/article.TECH178271.html
• Do these settings look correct for updating client definitions every 4 hours and does this pull from a GUP (this policy is for a remote site and uses a GUP)