SPI communication between PIC24FV32KA301 and MS5611 won't work
I probably should write this into a comment, but I don't have enough reputation to write comments, so here goes:

I have several devices in production use with both PIC24FV32KA301 and PIC24F32KA301 using SPI all over the place.

As far as I can tell from what you posted, your SPI usage looks sound.

Although the sensor datasheet doesn't state it, but the things I use SPI with usually require the CSB to be pulled high, maybe kept high a bit, then pulled low again between commands. You might try that...

Also the conversion supply current is measurably higher than the standby current. You may try to bombard the sensor with conversion commands and check the current to see if it gets/executes the commands at all.