After domain registration, you received an e-mail from RNIDS (Register of National Internet Domains of Serbia) containing a verification link to confirm the correctness of your e-mail address and contact information. The verification link is valid for 20 days from the registration of the domain. If the link is not clicked and the verification is confirmed within that period, the domain is suspended. When the domain is suspended, you can still click the verification link at any time (as long as the domain is registered) and then the domain is verified and goes into active state.
The subject of the email reads:
"domain name": Potvrda registracije domena / Domain Registration Confirmation
Please check your inbox (SPAM/Junk folder also just in case). Just click on the link in the e-mail and the domain will be activated. It will take about 30 minutes for the domain to be visible again on the Internet.