The Sales Opportunities tiles in Showroom, by default, will show one month of data.
This affects the 'My Opportunities' Tile and the 'Open Opportunities' Tile.
Users are able to view opportunities older than a month by using the filter option in the top right-hand corner:
Then select the required dates in the Opportunity Opened Between section:
If using the Sales+ app, users will not be able to view opportunities older than a month.