Nope, that's not what's going on. Citibank's archaic systems block you from doing anything new for 24hrs after you've cancelled a payment. Call it an anti-spam flooding measure if you like. It's undocumented and you won't get any acknowledgement of it existing from their CSR either, but it exists. This is why the advice is that if you want to cancel any scheduled payments, then make those cancellations the very LAST thing you do after you've set up the new ones, because once you cancel, you'll be locked out of doing anything more until tomorrow.
There are other 1 day lock outs for doing other things too. For example I transferred some money into my credit card to lift the available credit to an amount that would enable me to execute an FPO cash out to get a cheap eGift card. Doing that locked me out of starting that FPO until the next day too. Citibank's systems need to do a reconciliation 'reset' overnight before a lot of things will be allowed, but unless you work for the Citibank back office or are their IT person, you won't ever find a documented list of what all these triggers are. You only find out about them when you accidentally trigger one and suffer the 1 day lock out yourself.
Another particularly annoying lock-out trigger they have is the addition of a new payee. To any normal way of thinking, the only time anyone would want to add a new payee is when they actually want to USE that payee to pay money to immediately. Unfortunately Citibank's batsh!t systems are so utterly cough that adding a new payee will lock you out from using that new payee until the next day with an "error" that says FG1441. When you interrogate their CSR to explain what FG1441 means, they just feed you some BS scripted cough about fraud and security and health & safety and privacy and inclusiveness and climate change and same-sex marriage and whatever other wokist cause-du-jour they can come up with to deflect from the fact their systems are too cough to deal with more than one request every 24 hours.
You can sometimes reset the lock-out by logging out and back in again, but this doesn't work more often than it does. You can also force them to reset it if you can get transferred to the Security & Fraud Team who seem to hold the keys to this lock-out system, but it's actually impossible to talk to anyone in the fraud team directly. No CSR will ever put you through to this mysterious team. If you really ramp up the agro to DEFCON 11 and threaten a case with AFCA, someone will eventually clear to lock-out and clear the path forward… but, be warned, it will take at least an hour on chat or the phone before you can get to this.