Currently work on Windows 10 any MAPIEx works fine for me, generally. Sometimes seems to hang, but I think that more to do with my email account. Use 5.0.24 Blue Prism version, and may stay on this now!
May be worth you confirming that MAPIEx has been installed as per the guidelines on the install document. Only supported as 32-bit and you have to change a couple of settings somewhere to read from the correct directory. Assume you've tried and done that though?