Update powerapps-custom-visual.md

Clarifying when canvas apps embedded in Power BI visuals are accessible to guest users. Previously this was unsupported, but it is actually supported if the prerequisites are met.

Author: alaug

powerapps-docs/maker/canvas-apps/powerapps-custom-visual.md

@@ -72,7 +72,10 @@ Let's look at the steps required to use the Power Apps visual in your Power BI r
 The following limitations apply to the Power Apps visual:
 
 - The maximum number of records that can be passed from Power BI to Power Apps visual using "PowerBIIntegration" object is limited to 1000.
-- Power Apps visual isn't supported for [guest users](share-app-guests.md).
+- Power Apps visual is only supported for [guest users](share-app-guests.md) when the following conditions are met:
+- - The canvas app URI (weblink) includes the tenantId of the app in the query string.
+- - The Power BI portal authenticates the user. (It’s not configured to allow anonymous access.) 
+- - The canvas app is shared with the user/guest attempting to see the contents of the app. 
 - Power Apps visual doesn't support multi-level embedding of Power Apps in Sovereign clouds. For example, embedding a Power BI report with Power Apps visual to a SharePoint page, or further embedding that SharePoint page to a Teams channel isn't supported on sovereign clouds.
 - If you change the data fields associated with the visual, you must edit the app from within the Power BI service by selecting the ellipsis (...) and then selecting **Edit**. Otherwise, the changes won't be propagated to Power Apps, and the app will behave in unexpected ways.
 - The Power Apps visual can't trigger a refresh of Power BI reports and Power BI data sources from within Power BI Desktop. If you write back data from the app to the same data source as the report, your changes won't be reflected immediately in Power BI Desktop. Changes are reflected on the next scheduled refresh.
@@ -121,4 +124,4 @@ For more information, go to [Power BI Accessibility Documentation]( https://docs
 * Check out our [video](https://aka.ms/powerappscustomvisualvideo).
 
 
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