When I try to open my photos I get the message 'Photos cannot find the System Photo Library named Photos Library.photoslibrary; can anyone help me get my photos back please?

Just some food for thought: you could have run your System Photos library from the external drive is so desired by just opening it with Photos and continue with it on the EHD. That is only if the EHD is formatted APSF or OS X Extended (journaled).

Hi

Try holding down the option key while starting photos - more than one libray listed? Open each in turn until you find your photos.

Hi

I had the same issue and it turned out that I had accidentally moved my Photos Library.photoslibrary; to an external hard drive.

subsequently my mac could not find it.

i just moved back onto the mac and no problems now