Tag upload proven to be broken and customer support not available.
Dear customer support who is not managing to read incoming queries with the keywords "critical", "breakdown", "production stop":
Your tag upload is broken and just omits values upon import.
Because of that, our latest update of Projects (tags) to bill against is broken. Therefore we cannot use your service anymore.
Thank you for not even reading this in a timely manner.
In all honesty, just having a bot answer "We are really in trouble with our service, please be patient" would already be an improvement over "13 hours ago, not seen yet".
Also it might really be a great idea to simply categorize inbound tickets by criticality. There is great tools out there which do this out of the box for you - even with sentiment analysis. Just sorting by the customers plan or invoice volume would probably already help.
The last point: If you don't offer phone support or even escalation paths for your enterprise plan customers then at least get some proper SLAs into place. It's not that hard.