there're a few ways to embed your retool app, which one are you currently trying to use?
It sounds like you need to use the Retool Embed JS SDK. the github is over here
even though you're on the business plan, do keep in mind the little pricing caveat but especially remember that last sentence 
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I'm sure if you sent any of the Retool people a DM or tagged them asking what could be done if you fall into one of those situations given you're use case, they'd be happy to point ya in the right direction
related link: