Online errors: unknown resource
This is one of the most common errors for experiments which run locally but fail online. In the case of a spreadsheet the name of the spreadsheet is mentioned twice. In the case of an image, you see the name of the image component (ImageStim) and the name of the file (resources).
At the start of an online experiment you usually see a download bar for the resources.
However, at this stage PsychoPy only downloads files it can identify, either because they are specified in components, loops or spreadsheets. Resources it can’t identify automatically need to be added to the list manually. The easiest way to do this is via Experiment Settings / Online / Additional Resources.
Add resources using the plus and remove them with the minus. The three dots offer to add a custom item, but when I last explored this option it didn’t seem to work.
If you don’t want to download all resources, for example because each participant sees a subset of the stimuli, then you can download addition resources in code.