Custom blocks not working

Custom blocks not showing up on creative inventory. They're also unobtainable using commands. Turned on experimental gameplay, but blocks still not showing up.
Steps to reproduce:
        1. download any custom block addon from mcpedl or make one of yours
        2. create a world and apply the pack(with or without experimental gameplay)
        3. check the creative inventory or type /give @p <identifier of the custom block>