I believe this is related to an API bug, not CombatMaster. I'm getting the same error and I don't use that script. See <a href="https://app.roll20.net/forum/post/10911736/anybody-else-unable-to-spin-up-their-api-sandbox" rel="nofollow">https://app.roll20.net/forum/post/10911736/anybody-else-unable-to-spin-up-their-api-sandbox</a> for additional information.