Numerous causes can prevent you from starting a campaign on YTMonster.
The most likely cause is that your rank is Bronze.
At the current time, you must have a rank of Silver or higher to start campaigns. You can find a complete overview of the benefits and requirements of the ranks here.
Other possible causes include, but are not limited to:
Age-restricted video
Country-restricted video
Premiered videos
Number of the video's likes hidden
Number of the channel's subscribers hidden
A server-sided issue on YouTube and/or YTMonster
If you are unable to start a campaign while not falling under any of the above causes, you are more than welcome to contact us for further help.