Steven,
I have had this same problem where my account was blocked because of “suspicious activity”. This was cleared simply in a call on 150 and setting a new password.
On the call I asked about the “suspicious activity “ and having received an email stating that the account had been frozen because of “suspicious activity” I replied twice to ask for details of this “suspicious activity “? I cannot get an answer.
Any access to my email account is on devices with full live security cover (Bit Defender) and I have carried out full scans and checked my sent items. There are no issues and no sign of “suspicious activity “.
Please can you let the community know the nature of this “suspicious activity “?
Thanks