Hello,
I’m using the same TMS tag on my websites : www.site.eu, www.web.mobile.eu
I do it since several years without issues.
Through the Piwik Pro Chrome Plugin, I was able to debug my tags.
Since the new debug mode in the UI (et end of plugin), it no longers works on web.site.eu (but it works on www.site.eu)
It opens properly the web.site.eu page, but the console display the issue above.
Many thanks for your help
Hello @Valentin_W - welcome to our community. I cannot enter your website under web.site.eu - on main page site.eu it seems you have also added matomo.
Not sure if it will, but maybe this article can help you solve your issue:
web.mobile.eu is redirecting me to .de and I cannot check it
I have not shared the real URL 
We don’t use matomo, only piwik.
Send me your real URL in private message please, I can take a look
I don’t see Piwik PRO request in network parameters on your web. subdomain - it’s not loaded correctly. For some reason it’s loading consent on first visit, but doesn’t do anything else in background.
Please check if it’s installed correctly, that might be the reason why it’s not working now:
