I created a new Block programmatically with its controller and view. When I go into EPi Server Admin/Content Type I can see my new block.
When I'm trying to create a new page and insert the block, it doesnt appear in the list.
How does the ContentTypeAttribute for the block look in code? You should verify that AvailableInEditMode is not set to false.
Similarly, are you trying to create it in a specific ContentArea or just for the site in general? If it's for a ContentArea be aware that in code the ContentArea can be decorated with an AllowedTypesAttribute restricting which blocks it can contain.
I found it. The Block needed to implement IHomeSectionPageBlock interface to appear in the list.