You need to perform the following steps:
- Go to Setup > Search for Visualforce Pages in the Search Box.
- Search for the "AboutAutoNumber" page > Click "Security."
- Enable it for the required profiles > save.
P.S. Discover Auto Number Helper, the simple way to update Auto Number values in Salesforce. Find it on AppExchange - https://appexchange.salesforce.com/appxListingDetail?listingId=a0N30000000puTcEAI