Hi @jhawks
You don't need SDEHOME to be configured for FME to work. That is likely a misleading error message from the ArcObjects side (but lets see if that holds true after some other information)
What other tests have you completed to 'isolate' the issue?
Can you TNSPING the Oracle Server with the 64bit Oracle Client?
If there are multiple bit version of Oracle Client, ensure the 64bit is first.
What type of Oracle Client do you have installed? Instant (recommended) or Full?
If you have downloaded the SQLPlus Client (for Instant Client) or have Oracle Full Client (included) can you test with the 64bit Oracle client that you can connect to the Oracle Database?
Do you have TNS_ADMIN environment variable configured? This will instruct all Oracle Clients (Full & Instant), and thus FME uses the single tnsnames.ora file for resolving the TNS Alias.
In FME, try publishing a workspace with an Oracle Reader and use the syntax host:port/servicename to connect to the Oracle Database - this will bypass the need for a valid tnsnames.ora and may help identify an issue with the tnsnames.ora file being used by the Oracle Client to resolve the alias (especially if there are multiple Full Oracle Clients installed).
Since ArcGIS Desktop is 32bit that won't be helpful as it will be using the Oracle 32bit Client if installed.
You could also isloate 64bit ArcObjects by using arcpy 64bit via geoprocessing to make a connection with the 64bit oracle client but that is likely more effort than necessary.
There shouldn't be a problem with the configuration you have using.
Can TNSPIng, can connect thru SQL plus, only 64 bit oracle full client installed. Set TNSNAME to point to the TNSNAME.ORA File. Still no good.
Edit: Fixed! Had to reboot for patches, that likely applied environmental variables, all good now, thanks!
Great! Yes either restarting FME Desktop or restarting the FME Server Engine service would be required. However, typically the engines restart often enough that this just happens.
I'm surprised you needed to reboot but maybe the engine restart was the key...
During my testing yesterday I didn't have to do that, just restarting the engine service is enough to pick up the new environment variable and path updates.