I've never used this scenario before so I just tested the exact same scenario and it works correctly with two storage credentials using the same Access Connector:

cred1 → ext_1: abfss://data-test@data_test_storage.dfs.core.windows.net/path1/
cred2 → ext_2: abfss://data-test@data_test_storage.dfs.core.windows.net/path2/

Key points from my successful test:

• Same storage account + container (data-test@data_test_storage.
• Same Access Connector with Storage Blob Data Contributor role on entire storage account (not just container level)
• No path overlap between path1/ and path2/
• Same ADLS Gen2, same permissions, same workspace

Questions for troubleshooting your issue:

• Is the Access Connector permission assigned at storage account scope or just container level?
• Are both credentials using the exact same ADLS Gen2 storage account?
• Does cred_2 appear grayed out in Catalog Explorer (indicating workspace binding issue)?
• An most important Is this a privatized environment? If you have firewall enabled on the storage account, it can block access because the Access Connector can't reach from the matching network you're using to access this storage.