Instagram cannot connect to ManyChat despite Full Control / Full Access

Your Page connecting fine while Instagram won't is the useful part. That tells you your permissions and the ManyChat side are working, and the problem is specific to the Instagram account.

That first error is the clue. "You need full control of this business portfolio" is not talking about the portfolio you've been checking. It's talking about whichever portfolio owns the Instagram account, and an Instagram account can only live in one portfolio at a time. If yours was claimed by a different one, often an old portfolio or one Meta created automatically when the account was converted, you can hold Full Access on your main portfolio all day and it changes nothing.

Two things to check, in this order.

Open Instagram, Settings, and confirm the account is actually a Professional account, Business or Creator. A personal account cannot connect to any messaging tool, and the error you get is exactly this vague. Worth ten seconds to rule out.

Then open Meta Business Suite and look at how many Business Portfolios you're in. If there's more than one, find the one holding the Instagram account and check your access there specifically. That's the portfolio Meta is complaining about.

The "try again later" message is separate and usually genuinely transient on Meta's side, so retry once the above is sorted rather than reading anything into it.

My automations aren’t working either. They were working just fine, until last week. I have also refreshed permissions, granted full access, etc.  This is really frustrating. Sorry you’re in the same boat. 

Worth splitting this from Alexa's, they're not the same thing. She can't connect at all. Yours connected fine and then stopped.

One question gets you most of the way: is it failing for everyone, or only for people who've never interacted with you before? If your long time followers still get the DM and new commenters get nothing, that's your contact limit rather than anything being broken. ManyChat keeps serving people already in your list for the billing cycle and quietly stops admitting new ones, so it looks like a partial failure instead of a wall. Settings, Billing, Subscription shows where you are.

If it's failing for absolutely everyone, including people already in your list, that's a different thing and more likely Meta side. Refreshing permissions won't touch it and a ticket won't move fast on it either.

Either way, check whether the keyword comments are still visible when you're logged out. A hidden comment never generates the event at all, so the automation never hears about it.