Hosted feature layer with a high number of points and custom symbology is not visible in ArcGIS Online Map Viewer when using the Chrome or Edge web browser.
This issue is not reproducible in ArcGIS Online. If the issue occurs, contact Esri Support Services as additional information is required for further investigation.
解决办法
Use Map Viewer Classic in any browser, or use Map Viewer specifically through the Mozilla web browser.
The symbology of the test layer is visible only in Map Viewer when accessed via the Mozilla web browser.