Try a child's sized potty seat for the floor, rather than using the grown up toilet with an adapter. Your child will feel a sense of balance when he can plant his feet firmly on the floor. You may also want to flush after your child has left the bathroom. Wail until naptime or a time when he is distracted elsewhere before flushing the toilet. Remember not to pressure your child.
Some children get a sense of security from diapers and the attention they get while being changed.
Be sure to provide extra one on one time to replace that playtime on the changing table. Backsliding - Your child has been potty trained for some time and suddenly begins having accidents. This can occur due to several reasons. For some children this competition for attention causes regression to babyhood for the older child. Adjusting to new situations and the loss of a parent can also cause children to backslide.