There are two issues revealed in May 2026 version of Power BI Desktop RS app when working with "Oracle Database" data source.
[1] From May 2026 version Power BI Desktop RS cannot connect to TNS names from tnsnames.ora that linked using instruction "IFILE" (include from external file):
IFILE = N:\DBA\Oracle\additional_tnsnames.ora
January 2026 version can work with such external TNS names (although Report Builder never can).
[2] From May 2026 verson Power BI Desktop RS cannot connect to some usual TNS names that worked before. It returns strange Oracle error "Oracle: ORA-01017: invalid username/password; logon denied". But in fact credentials are correct, server is available. You can rollback Power BI Desktop RS to January 2026 version and same connection works again.
Problems above looks like some new bug in "Oracle Database" data source type.
