Problem solved by calling the Chromecast customer service. For future reference, whoever needs it:
Disconnect Chromecast from power Disconnect Router from power After 10 seconds connect router to power After 1 minute connect Chromecast to power Once the Chromecast photos start running, wait 10 seconds and then cast your tab.
If this didn't help, they suggested going to your router settings and change to channel 9 or 11.