rfranco1 Can you confirm if you have the following dependency in your plugin xml file? It should be included within the web-resource element that houses the js files that require the date picker.
<web-resource ...>
...
<dependency>com.atlassian.auiplugin:aui-date-picker</dependency>
</web-resource>
Additionally, can you also double check that the date picker function you are using in your latest code is $.datePicker with a capital 'P'. It seems to be so in your latest screenshots, but I am seeing the lower case implementation in the Jar for the plugin. The lower case version refers to the standard jQuery UI implementation.
It might just be that you are missing the dependency to the date-picker resources. Some other aspects of Confluence also require the datepicker, but where before it might have been included on the page by chance, we now aim to define all of our dependencies explicitly. Some of the code that may have been present on the page in earlier versions of Confluence may now be loaded asynchronously, so it's possible that the Date Picker js is loaded onto the page at some point but not as early as it may have been in previous versions. This may be why you are seeing it transparent at first but displaying properly if you add a delay.
In the AUI documentation, you'll notice that not all the components are included in core, and an explicit dependency should be defined to ensure that the components will continue to work. For instance, the Date Picker is one of those components.
https://docs.atlassian.com/aui/latest/docs/date-picker.html
It may also be worth your time to double-check the AUI components that you are using in the plugin, and to make sure that explicit dependencies are provided for those components that require them.
Please let me know if adding the dependency and double-checking the 'datePicker' text case solves this issue.
Perfect Alex! Well done!
Thanks for your support