Thank you for contacting the Intel community.
The MAXIMUS IX HERO ATX has different chipset than the one on which the RAID volume was created, so you will not be able to boot from this RAID volume, at this point, I suggest you to back up your information and then create the RAID volume again.
Another thing you can try is, install an operating system on a non-RAID hard drive or a new RAID volume and access the contents of the original RAID volume from within that operating system.
Now, since these two motherboards are ASUS motherboards, I suggest you to contact ASUS and ask for more information about it, perhaps they can have other suggestions and support to provide you.
I'm sorry. I forgot to mention the Raid 5 array is only a data drive. I have a SSD as my primary boot drive for windows 10. Does this change the outcome or would I still be better off backing up the array and starting fresh?
Please bear in mind that a RAID is not a back up so we always suggest to back up the information to avoid lose of data.
At this point, you can try accessing the information from your SSD but if it is not possible because the RAID was created on another motherboard with different chipset you will need to create the RAID again.
Before doing so, back up your information.