SINGAPORE - Fresh SingPass problems have surfaced after initial teething issues brought about by "heavy traffic" to the new authentication system were resolved on Monday.

The enhanced SingPass was just rolled out on Sunday to better protect some 100 e-services - such as those which deal with personal, financial or health data - from 60 government agencies.

But some users who had opted to use its new security feature - a one-time password (OTP) generated randomly on a calculator-like token or delivered by SMS - in addition to the usual SingPass and user name were left high and dry.

As early as 8am on Wednesday morning, some users were complaining about not being able to link their token to the enhanced SingPass system on the latter's website.

Others who had linked their phone number and token to the enhanced SingPass system complained they were locked out of e-government transactions on Tuesday night.

The problem was due to not being able to receive the OTP via SMS despite making numberous requests for it to be sent.

Frustrated, some users switched to using the token, but this message popped up on their computer screens after three failed attempts with the token-generated OTP: "You have entered an incorrect/expired one-time password. Please try again."

On Monday, applicants for the new SingPass were unable to sign up for their enhanced accounts. Users who tried to access the SingPass website between 10am and noon were unable to do so. A message on the website said that maintenance was in progress.