I have also received this email claiming that I am close to my POT limit. It also says that future transaction may be declined. I have gone over my POT limit by about $300 without issues and I believe I could keep going. Also I pay in full so it doesn't bother me. Next month i'll keep spending without mid cycle payments to see what happens.
I wouldn't say that's ambiguous, it just means that you have hit your current internal spending limit for NPSL - the limit isn't preset, but everyone does have a limit somewhere. Amex is not telling you that your account is frozen nor does it mean you are about be hit with a Financial Review. It means exactly what they stated: further charges may or may not be approved until a payment has been made to bring your current balance down. You've not experienced this from other card issuers because you had a credit limit issued and made known to you with them.
@Credit12Fico wrote:"We recently approved a transaction on your account. However, it is important that you make a payment on your account soon to continue to enjoy uninterrupted use of your Card."
I received this ambiguous email message from Amex relating to my platinum charge card with pay over time disabled after I made a 5K purchase. I searched and there are two other threads who describe receiving the message, but I did not figure out from those two threads what exactly this message requires me to do and what the consequences are for ignoring the message? I've never been harrased before by any other bank in the middle of a cycle for a "payment".
I did not intend on paying anything until just before statement closing which is end of february. Is Amex telling me my account is frozen? Will further charges go through without payment. Will I invite a financial review?
No they're not telling you that the account will be frozen, and they're not telling you that there will be a financial review, but they are telling you that further charges may not be approved. They like to keep you guessing.
Personally I find that kind of uncertainty abhorrent, and this is one of the reasons I don't have any Amex charge cards.
@FinStar wrote:Harassment or a courteous reminder?🤔
How often do you make such transactions per month on your Platinum Card? Did you voluntarily disable the POT feature or was this suspended by AENB?
Bottom line, do not ignore the messages/reminders and PIF as soon as practical. Otherwise, you can risk AENB placing a hard limit on your card.
Harassment 
. I don't want to hear from them unless I've done something wrong. They shouldn't have approved the charge if they were going to ask me to pay it off immediately. I would have put it on another card so i would not have to pay it off.
Looks like you've found out that your "internal NPSL" "Limit" is only $5,000.
With that said they aren't "harrassing you for a payment" as you said. They are simply telling you that you have reached your internal max spending limit on the card and that for any other charges in this billing cycle to be approved (if you so wish) that you'd need to pay down that $5,000 amount (again if you so wish). Otherwise just don't use the card and pay on the due date.
@Credit12Fico wrote:Harassment
They are not asking you to pay it immediately. You are not required to pay it until the due date on your next statement where this charge appears. You are only required to make a payment if you wish to continue making additional charges.
@Credit12Fico wrote:
@K-in-Boston wrote:I wouldn't say that's ambiguous,
"However, it is important that you make a payment on your account soon to continue to enjoy uninterrupted use of your Card."
That's fairly ambiguous to me. They could have put a dollar amount of remaining spend before they "interrupt" my use of the card.
Amex doesn't disclose spending limits like this. Also, you may have pending charges or credits they could not account for at the time of the automated email and the spending limit is dynamic so by the time you read the email your internal limit may have changed. Your spending limit is ambiguous (that is the point of NPSL; if it were not ambiguous they would just issue a credit limit as they do on revolving products or when a hard limit has been placed on charge cards).
@bigseegar wrote:Looks like you've found out that your "internal NPSL" "Limit" is only $5,000.
Or $5,000 plus the balance of all other unpaid transactions, pending transactions, fees, or holds.