DataSource.Error: An error happened while reading data from the provider

Hi remyc - Verify that the correct version of Oracle Data Access Client (ODAC) or Oracle Instant Client is installed. Both Oracle and Power BI should be 64-bit versions, which you've already confirmed.
If you reinstalled Oracle, ensure that the PATH environment variable includes the path to the bin directory of your Oracle installation (for example, C:\Oracle\product\12.2.0\client_1\bin).

Verify that the correct version of Oracle Data Access Client (ODAC) or Oracle Instant Client is installed. Both Oracle and Power BI should be 64-bit versions, which you've already confirmed.
If you reinstalled Oracle, ensure that the PATH environment variable includes the path to the bin directory of your Oracle installation (for example, C:\Oracle\product\12.2.0\client_1\bin).

checking logs from both Oracle and Power BI might give more detailed insight into the root cause.

reference solved threads FYR:

Solved: PowerBI desktop 64Bit oracle connection error Obj... - Microsoft Fabric Community

Solved: Oracle: Object reference not set to an instance of... - Microsoft Fabric Community

Solved: Re: PowerBI desktop 64Bit oracle connection error ... - Microsoft Fabric Community

Object reference not set to an instance of an obje... - Microsoft Fabric Community

Solved: Re: Oracle: Object reference not set to an instanc... - Microsoft Fabric Community

Hope the above information helps.