When creating MCS catalog for Azure, master image need to be selected from its Resource Group.
While doing this, some Resource Groups are visible, and some others are not. All visible and non-visible Resource Groups were created manually and they all were working fine during initial deployment. But some of them are not visible on Studio anymore after some days.

The affected Resource Groups are neither visible in Studio nor in PoSh SDK (image.folder location in XDHyp: Posh drive). However, if we know the Resource Group name, can browse to them by typing the name manually in PoSh SDK. Subscription scope service principal is used for all Resource Groups, and we are also able to browse to them in PoSh SDK. So it is not an access related issue.

If we create new Resource Groups, they are all visible on Studio for master image selection.
 

Check the tags on Resource Groups and compare them with 'visible' Resource groups.
Delete Citrix related tags from the Resource Group if they are present.
Presence of Citrix related tags can lead to this problem as explained on 'Problem Cause' section of this article.
 

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Problem Cause

Studio is designed to list only manually created Resource Groups for master image selection. If the Resource Group was used for any other Citrix activities that creates Citrix tags on them, then they won't be visible further for master image selection window. Tags on Resource Groups are checked during enumeration and if there is any Citrix related tags as given in following example, they are ignored from displaying in Studio.