Fresh SingPass problems have surfaced, after teething issues brought on by "heavy traffic" to the new authentication system were resolved on Monday.
The enhanced SingPass was rolled out on Sunday to better protect some 100 e-services by 60 government agencies.
But some users who had opted to use its new security feature - a one-time password generated randomly on a calculator-like token or delivered by SMS - in addition to the usual SingPass and user name were left flustered.
As early as 8am yesterday morning, some users complained of being unable 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 that they were locked out of e-government transactions on Tuesday night.
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