I set up a tropical weather monitoring dashboard based on this blog article from Esri: Updated Arcade Code for Scaling Symbology
When setting the map symbols using images stored online, the symbols would often stop displaying either over time, or depending on the computer or browser displaying the map.
On all PCs/browsers tested, I was logged into my organization with my account (the account that created the items). I tried sharing the map, layers, and dashboard with Everyone. I also tried uploading the symbols to my organization, and sharing them with Everyone. To troubleshoot, I also tried disabling any browser extensions and lowering my security settings.
Below is a screenshot I took showing the blank symbols. I've tried several times to set the symbols, but they keep disappearing.