Hi, Uku-Mats
you have extended the Deadline to Sunday, September 2, 2018 UTC but on designers' side Project status looks - Closed (Pending Selection) thus new designers can't submit their ideas.

Maybe you see project status as "Open - Deciding" from your customer account
yet if you put (+enter) contest link in browser not being logged in the account -- then you see - "Closed (Pending Selection)".

The project deadline extension add-on working badly, sometimes
Designcrowd support can fix this issue --- ask them just to re-open the contest
This method helped with another project that had this error

Hi Project Owner
Could you mention the band name and name of products here
Thanks in advance

With Regards,
Seema