Problems with a Microsoft website has left some business customers unable to activate and use their Microsoft software for more than a month.
Microsoft first took down its Volume Licencing Service Center for maintenance in early December, after attempts to merge multiple licencing sites into a single, more secure site backfired for some users.
Those affected include businesses purchasing Microsoft software, or resellers and integrators handling newly-purchased software for business customers.
Problems they have reported via Twitter include users losing access to paid-for software licences; an inability to login to the VLSC site and fix this for one month or more and six-hour waits on Microsoft telephone support trying to fix their accounts.
One user said that Microsoft, unable to grant him access to his account and licence activation keys, was forced to physically mail him replacement software.
In a blog, Microsoft "sincerely apologised" for the "inconvenience".
"While the vast majority of partners and customers are able to access the system, there remain some customers who may be experiencing difficulties and it has taken us longer than expected to correct those issues," said Microsoft.
It invited users to send problems via email or Twitter.
Some customers are finally getting their problems solved. Mark Lowe, co-owner of a Raleigh, a systems integrator, tweeted that he "was back on track" after working with Microsoft's Twitter-based support team.
Lowe confirmed that he had, as per earlier tweets, been "going insane" after being unable to gain access to software that he had purchased more than a month ago - and after spending hours with Microsoft's customer support.
With his licence problem fixed, "I am a happy bunny today ," Lowe said in a tweet.