If you’re trying to interact with a new or obscure token, it may not have been added to the user interface yet. You should be able to interact with this token by entering its address (ex. 0xba100000625a3754423978a60c9317c58a424e3D):
It’s also possible that a specific token is incompatible with the current version of Balancer. Tokens that don’t conform to the ERC20 standard (ex. tokens that don’t return bools for transfer() and transferFrom() functions) are not supported, but should be supported in future releases. As of writing, tokens that do not conform to these standards will NOT be added to the UI whitelist.
To get a token added to the user interface, swing by the #token-requests channel on our Discord (https://discord.com/invite/ARJWaeF). To streamline things, come armed with coingecko and etherscan links for the token contract.