It seems that with the February 2024 ArcGIS Online update to dashboards, you can no longer pass the URL to an image using an attribute expression.
Below is an example where if I insert an image using the "Insert Image via URL" tool, it works. But, if I use the same URL as an attribute expression, the image is not displayed.
Prior to the February 2024 update, this definitely worked, as we would swap in the URL to various images based on attribute expressions.
Attribute expression created

HTML used --- swapped out the hard-coded URL with the attribute expression

Hard-coded image is returned, attribute expression is NOT returned.
