I have a lvl 8 cleric and took the magic initiate wizard feat for booming blade. But it does not roll the 2d8 in roll 20. It rolls 2d8 for if the target moves but only 1d8 for the hit. If I am correct it should roll 2d8 on a hit as my character level is level 8. I also looked to see if  i could change this manually but did not see anything. Am I right? Should it be rolling 2d8 on the hit? And is there any way to manually override this.

Forgive me, are you asking about a system on Roll20 and not on Dndbeyond?

Booming Blade doesn't deal damage as part of the attack until level 5, then that increases to 2d8 at level 11 etc

Conal and Golaryn have this, so my post here is more for my killing time until the microwave pings my nommies.

1st thing: Booming Blade does damage "on hit" and "on move". The "on hit" damage is 0. The damage for hitting is whatever the damage is for the weapon you used for the attack. The damage on move is 1d8.

Both damages increase by 1d8 at 5th level, 11th level and 17th level. For your 8th level character this would be +1d8. So your on hit becomes 1d8 (in addition to the weapon damage) and the on move becomes 2d8. 

So it seems to be rolling perfectly correct.

2nd thing: Roll20 is a different company to D&D Beyond. Both Roll20 and D&D beyond are separate from WotC. Even if something were wrong, there's nothing we can do to help you. D&D Beyond cannot do anything with or for Roll20. If you need help using Roll20 features they do have community forums and a wiki page with a lot of useful information there. That should be where you ask for help regarding Roll20 behaviour. It would be highly unlikely any dev of Roll20 would be on here since D&D Beyond and Roll20 are competitors in many ways. It's like going to Microsoft Xbox asking for help with the Sony Playstation settings.

AHHh. Ok, thank you. I was reading it wrong. I thought it said it dealt and additional 1d8 below 5. And yes I was asking about both as my beyond character sheet is tied to roll 20.