Do nonprofits need to register with the Attorney General's office in every state they receive donations from?

And what if they don't know where the donations come from? Are they required to register in every state just in case?

If a nonprofit organization solicits funds from people in other states, the organization may need to register with those states to be in compliance with local laws. Giving USA Foundation publishes and sells an Annual Survey of State Laws Regulating Charitable Solicitations as of January 1, 2018.  The survey includes State Regulatory Agency information for each state, registration requirements and other useful information.