@Edent I didn't write it. However, quite simply, if you got the email, then your previous password has been invalidated. Reset it to get back in.
@otto42 perhaps you could pass on some feedback that it is a *very* poorly worded email.
Does anything stop me re-using my old password?
@Edent if its a good password, no. However, it will not allow use of pws found in other data breaches such as the haveibeenpwned set.