Have you tested your Snowflake connection in ODBC 64? The usual cause for this is that your username in ODBC 64 is not the same as your username in Snowflake (or your username in Alteryx is not the same as your ODBC64 username). Often this is different domains in the email or you are authing with your full email (identifier@domain) --- when you only need to auth with your indentifier. either way ---> you should be able to solve this by having your username you are setting up in Alteryx tie into your working username in your ODBC64 set up.
Note ---> I assumed that you auth into Snowflake via SSO (and that you are currently logged into Snowflake as you - vs as service account) --- assuming you are using a session token/Snowflake requires the user who auths via ODBC to be the same who is logged in in the console when using a session token. (one user/one session token).