YouTube restricts the amount of activity that can occur from your account and/or network - IP address. These restrictions occur whether you are using Tube Toolbox or manually sending/sharing from YouTube's website. One of the primary benefits of Tube Toolbox is we handle the waiting and retrying.
When you have too much activity, YouTube will either send back a message saying you have to wait a while before trying again. Or, they will tell you the message was sent successfully when they did not actually send the message. Yes, that's right, YouTube will display a message "Your message sent successfully" even though they did not deliver the message to the recipient. The only way you can verify that the message was actually sent is by looking at your Outbox and verifying the message sent is there (which we do in Tube Toolbox).
Below are some links to YouTube support posts expressing frustration at the limited number of messages that can be sent.
YouTube previously (4th quarter 2011) instituted new sending restrictions. Please review this blog entry for a description of the changes. It is very important that you review the section discussing waiting 24 hours before sending again. If you are experiencing very few messages being sent, you should not try to send anything for at least 24 hours (both from Tube Toolbox and directly through www.youtube.com)
Tube Toolbox Handling Process
When we receive a message from YouTube saying you need to wait before sending again or the message is not in your Outbox, our software displays a message saying "waiting for restriction to be removed" or "YouTube did not send message". When this occurs we wait the maximum delay time as a default before we try sending again.
We have two delay settings that you control. The first set is the minimum and maximum delays. These settings govern how long we wait between trying to send messages/sharing videos. We recommend you leave our default settings of a minimum of 30 seconds and a maximum of 60 seconds as they meet YouTube's terms of service. These settings can be changed on the Sending screen (see screenshot below).
The second set of delay settings govern how long to wait after we receive a message stating there has been too much activity from your account. We suggest you set the minimum time to 15 minutes and the maximum time to 16 minutes. This setting is done by clicking on Options/Settings: