Hello Andrew,
I couldn't find the part number
SPA-1XTENGE-XFP
in current 12000 XR datasheets.
there is a part number for standard LAN 10GE with XFP optics. There are other two SPAs but one for DWDM has built optics and the other one is only for POS OC 192
generally speaking the optics
XFP-10GLR-OC192SR should be for WAN PHY
so the issue may be that the SPA does not support it
Hope to help
Giuseppe