Update: Issue has been resolved July 2017!
If you are anything like us, you embedded Google Tag Manager only to find out you cannot test your tags in preview mode. Rumor has it, Google changed a setting (we are unsure of which one) affecting your browser cache. Thus, the easiest way to get your website into preview mode as of June 2017, is to do the following:
- Login into Google Tag Manager
- Click Preview
- Open your website
- Check back in 15 minutes
Once this is complete, you may need to refresh your webpage after the 15 minutes, but preview should work. At least this process worked for us. If you have any ideas regarding browser settings, etc. that might speed up this process please share.