I tried all your points, still having the error.
Here the JSON file: http://safeyourfiles.tk/55507d3f14daf
Please try with creating new API Key for Browser, w/o restrictions. Type of error you experiencing is:
<!-- YTC ERROR:
domain: usageLimits
reason: ipRefererBlocked
message: There is a per-IP or per-Referer restriction configured on your API key and the request does not match these restrictions. Please use the Google Developers Console to update your API key configuration if request from this IP or referer should be allowed.
-->
And we don’t have solution for that at the moment. It’s on Google side (Google does not see that restrictions for key are disabled).
I choosed Key for browser and did not filled any urls in the box. I left it blank, still the error.
Do you uses Jetpack and Protection sub-plugin?
@relsimaron regarding this JSON configuration, you have set “SindppdRS” as Channel ID, and that is wrong. Please read https://wordpress.org/support/topic/ytc3-read-before-you-post-support-question-or-report-bug
I use Jetpack, but no Protection sub-plugins. But your plugin worked all the time with Jetpack until stupid Youtube had to change the API. But stil it don’t work.
@hartvanleiden Now I see different error:
<!-- YTC ERROR:
domain: youtube.search
reason: invalidChannelId
message: Invalid channel.
tip: You have set wrong Channel ID. Fix that in General plugin settings, Widget and/or shortcode. Check https://wordpress.org/plugins/youtube-channel/faq/
-->
So, API Key now works, but you have different issue.
On your website http://hartvanleiden.org/ I see that you use YTC Widget with ID13, and in that widget you set for Channel ID “PolitieRRoost”. This is wrong, so please set proper Channel ID.
Cheers
