You're not asking.
You're not inviting people to join your team. Week in, week out, you've got to invite, invite, invite. You have not because you ask not. The best way to build a volunteer team is personal 1-on-1 invites.
You're not praying for volunteers.
What did Jesus say to do when the "laborers are few?" He told us to, "pray to the Lord of the harvest that He would send laborers into His harvest fields.
Spend time each day asking God to send you volunteers. Jesus wouldn't ask us to pray for something He didn't intend on giving us.
You're not casting vision.
People are drawn toward vision. Stop using words like, "need...help...please..." and start using words like, "impact...opportunity...make a difference."
You're not getting out of the kid world.
You have to go where adults are if you want them to join your team. Get into the adult world. Show up for new member's class, visit adult Bible study groups, connect with the men's and women's ministry.
You're not partnering with the student ministry leaders.
Student volunteers are the bomb. You should have lots of student ministry volunteers serving in your children's ministry. If you don't, then reach out to your student ministry leaders and ask how you can partner with them to get students involved.
You're not keeping the volunteers you already have.
If you're having constant volunteer turnover, then it will be hard to maintain enough volunteers. How do you keep them?
Two words. Family and Fun. Family - people stay where they feel connected and have relationships. Foster this. Fun - people stay where they enjoy being. Work hard to create a culture of fun.
You're not effectively following up with people who have served one time.
There are certain times of the year when people serve in children's ministry one time.
Normally this is during a church-wide push for an event or special services. Easter services....Christmas events...VBS...camps...fall festivals, etc.
Have a strategy to go after the people who sign up to serve that one time. You can turn one-time servers into full-time servers if you're intentional about looping back with them.
You're not providing enough entry level positions.
More jobs = more volunteers. Especially entry level positions.
Not everyone wants to start out teaching, leading worship, or overseeing a program. Provide lots of easy, entry level positions. You'll find that people start out in these entry level positions, but down the road gain enough confidence and experience to step into a bigger role.
You're not in a church that has a culture of serving.
Look around. If all the ministries in your church are lean on volunteers, you may be in a church where serving is not embedded in the DNA.
You're not encouraging your current volunteers to invite people to join them.
Encourage your current volunteers to invite people to serve with them. They know people you don't know and have influence you don't have.
If you don't have enough volunteers, don't beat yourself up. You're not alone. I don't know anyone who doesn't need more volunteers. I have a lot of volunteers, but I need a lot more...and always will.
The key is eliminating road blocks like the ones you've just read about.