I had an Access Investing account open for ~8 months that ended in the middle of last year when MS decided to close it because of a low balance without warning. I had $1 in the account.

Just received a similar notice from Amex about closing my cards (I have the platinum and the standard version), so decided to try to open a new account through the MS interface, through which I deposited... another dollar.

Shortly thereafter I received an email from MS that says "we received your deposit", and I then spoke with the people at Amex (call the number on the back of the Platinum) who were very friendly, but they seem to have no insight into the MS account, including whether it is open or what the balance is. They said that it should be fine. I guess we will see.