Board Thread:Support/@comment-24856586-20140423230210/@comment-3153244-20140425140953

This bug is usually due one or more of the following reasons:
 * Your ally began the Co-op game in a higher quality than you. Thus your tower placement is seemingly impossible in their point of view and is not allowed.
 * Your connection is unstable (resulting usually in a laggy game). I do not know why this affects the gameplay, but it has occurred to me many times.