Accepted federal refund now delayed

I am a single person with no children/dependents. I e-filed my federal return on January 14th. I received notification that my return was accepted on January 17th. I signed up for direct deposit. Today I checked the IRS "where's my refund?" and it says there is a delay in processing my refund with a 1541 reference code. What could this mean? My return is honestly very straightforward so I am not sure what could be holding it up.