Dayana Yastremska's bid to have her provisional doping suspension lifted has been rejected by the International Tennis Federation (ITF).
The Ukrainian denied using performance-enhancing drugs despite testing positive for mesterolone metabolite, an anabolic agent, in November.
Despite the ban, she had travelled to Melbourne for the Australian Open.
Yastremska, who has been ranked as high as 21 in the world, previously suggested the positive test was the result of a "contamination event".
The ITF's decision to dismiss Yastremska's application is subject to appeal to the Court of Arbitration for Sport.
Australian Open updates
One case of Covid-19 among those in quarantine before the Australian Open - the first Grand Slam of the year - has been re-classified as negative.