@paul2009 thanks for looking into this. I am still unable to replicate your success. I have an unlinked page (https://www.snowballentertainment.com/twitter) to try and explain / show my clients a number of different options that are available with https://publish.twitter.com/#. When I use the tool it shows my feed but when I embed I get the 'Nothing to see here - yet' message.
I'm sure you are right about privacy tools but I can't seem to fix it. I have already disabled (not uninstalled) Ad Blocker Plus in Chrome and Firefox for my domain and no success. I also tried with Edge that has zero extensions at all and still the same issue.
Am I missing a potential system wide privacy tool on Windows?
If I am struggling then I fear my clients and visitors will too, and there is a high risk of visitors see the ugly / broken looking error message which is more damaging to clients tan simply avoiding and just having a button or fake image as placeholder.
Any more thought form you or others greatly welcomed!
Many thanks