After making changes to asset attributes, you'll often need to reindex your assets for the changes to take effect.
Asset Bank builds up an index from data in the database or filesystem to speed up searching or browsing. When you perform a search or you browse within categories or access levels Asset Bank is using the information in that index to pull the results.
A reindex is rebuilding that index from the file data and metadata stored as attributes. So when you make changes to how attributes work (whether they're mandatory, required for completeness etc) you need to reindex so that those changes are reflected when searching or browsing.
To do this, log into your Asset bank as an admin users and navigate to Admin > Attributes > Manage Attributes. The link to run a reindex is in the top paragraph and called 'reindex existing assets'.
There are two options, online and offline.
1 - Online Reindex
With an online reindex, the index for each asset is rebuilt individually. It makes the reindex process slower overall, but also means that the majority of your assets will be available while the process runs.
2- Offline Reindex
An offline reindex removes the index for all assets, and then as each asset is reindexed it will reappear in your Asset Bank. Although the process is faster, with an offline reindex your assets won't be available until they've been reindexed, therefore this type of reindex is more disruptive.