ASP.NET won't connect to Oracle via SSL, console app will. What's different?

I am trying to connect to a client's Oracle database over SSL using the managed ODP.NET provider. The client has provided a self-signed certificate which I have imported on the server. To test the connection, I created a console app which simply opens the connection then closes it. This works successfully. However, when trying the same simple connection from ASP.NET on the same server, I always get this error:

Oracle.ManagedDataAccess.Client.OracleException (0x80004005): Network Transport: SSL failure in parsing wallet location ---> 
OracleInternal.Network.NetworkException (0xFFFFE700): Network Transport: SSL failure in parsing wallet location

Here is the connection string:

Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL = TCPS)(HOST = xxx.xx.xx.xxx)(PORT = 3484))(CONNECT_DATA=(SERVER = DEDICATED)(SERVICE_NAME = TEST.CLIENT.COM)(SID = TEST))); User Id = userid; Password = pa55word;

In the config files, I point to a directory for the SQLNET settings:

<oracle.manageddataaccess.client>
  <version number="*">
    <settings>
      <setting name="TNS_ADMIN" value="C:\Oracle\tnsfiles" />
    </settings>
  </version>
</oracle.manageddataaccess.client>

And finally these settings from sqlnet.ora in that directory:

SQLNET.AUTHENTICATION_SERVICES=(BEQ,TCPS)
ENCRYPTION_WALLET_LOCATION = (SOURCE=(METHOD=MCS))
WALLET_LOCATION= (SOURCE=(METHOD=MCS))
SSL_CLIENT_AUTHENTICATION = FALSE
SSL_VERSION = 1.2

Is there any reason why the connection from the console app succeeds, but from ASP.NET it fails on a wallet error? They are using the exact same settings. I tried a lot of different things but I welcome any suggestions.