NetSuite two-factor authentication does not support RESTlets, which are used to integrate Bill.com with NetSuite. This is a limitation due to NetSuite's restriction of the usage of two-factor authentication.
If two-factor authentication is enabled in NetSuite, the following error message will occur after connecting the sync in Bill.com:
The two-factor authentication feature is not compatible with web services or SuiteAnalytics Connect. Likewise, access for Contacts is not supported by two-factor authentication using RSA tokens. To sync, users must connect via the native NetSuite admin login that does not have two-factor authentication enabled.
For more information, please refer to https://system.na1.netsuite.com/app/help/helpcenter.nl?fid=chapter_4247329078.html