Hey there Rix95,
I apologize for the late response, thank you for being patient! Were you able to fix that connection issue? If not, I'd be happy to help out, as these networking issues can be tricky. So, the Chromecast devices are made to work on the lower bands, the range being from 36-48. Currently, they do not connect to a higher network band, so you'll need to use those lower ranges.
I look forward to your response, and if you have any other questions or concerns for me, please let me know!