iFrame plugin has suddenly stopped working


For my university project I have made a simple website displaying some line graphs created on Grafana from a MySQL database. After leaving the site untouched for about 2 weeks, I have come back to find that the embedded iFrames are no longer working. They initially load up when the site is visited, prompting for the user to log in to Grafana to view the content but when the log in button is pressed, it shows this error: image
Does anyone have an idea what might be causing this? The link used in the iFrame code is still working when I paste it directly into the browser and I have also tried generating a new embedding code but none of these have solved the issue.

Any advice would be appreciated.

Many thanks,