I have been having issues with getting the RA8875 unit and the VS1053 working with the MKR1000.
I read online that the RA8875 does not play well with others and required a tri-state buffer to work with other devices such as the VS1053.
Just to see what would happen, I connected the RA8875 and VS1053 to my older board, the UNO.
I ran an INO file that utilized both devices and the display worked and the audio played.
Since they both work on the UNO, I will hook them back up to the MKR1000, check voltages and determine if the power is too low to cause the VS1053 board to work properly which could be causing the issue.
If the voltages are correct and not the issue, I purchased and should receive today some Tri-state buffers today that I can put in line with the RA and VS modules to see if that corrects the problem.
Either way, I will know after I get back from class today and let everyone know what the outcome is!