Owners of Jawbone fitness trackers are complaining on social media that the firm's customer support has vanished.
At the time of writing, Jawbone's Twitter and Facebook support accounts had not been updated for several weeks.
Some customers say their emails are not being answered either, and the UK helpline has a recorded message saying customer service is not currently available in the UK or EU.
A spokesman told the BBC customer care is "days from being back online".
He added that the firm was "in a process of transition".
Lisa Cope shared an email she sent the firm in December 2016 saying she had been unable to use her Jawbone since the summer following various issues with the tracker not working properly and problems charging the device.
She said she has not yet had a reply.
"I loved the Jawbone until it stopped working," she said.
"I thought it was a very good product and app, but had lots of flaws. I'm disgusted that they think they can just stop customer service even though they're still operational."
Rebecca Wire said her Jawbone Up2 was successfully replaced last year but the replacement is now being held together with gaffer tape and she has had no contact with the firm for over a month.
Lisa Davidson said her new fitness tracker stopped syncing with her phone after five weeks and she has also been unable to contact Jawbone.
"I regret not buying a Fitbit now," she told us.
The firm is currently scoring 0.4 out of a possible 10 on company review website TrustPilot, with 170 reviews.
TechCrunch reported in February that Jawbone - once a popular fitness tracker brand - intended to leave the consumer market and focus on healthcare providers.
However its wrist bands are still widely available. The Up3 is currently on sale for £53.99 on Amazon in the UK.
"I think Jawbone is not sure how to move forward," said Carolina Milanesi, analyst at Creative Strategies.
"The mainstream consumer market right now is a cut-throat business and the high-end is controlled by Apple so looking at the medical sector might seem an option - but I am just not sure they have skills that would set them apart.
"Jawbone might say they are coming back to wearables but it is hard to see how they could do that successfully. If they wanted to stop and regroup that was fine but we should have seen something by now."