My 11:05 flight on 1 July from LIS to LHR has been cancelled

Online no options were offered, I had to phone and the only option was a late night BA flight which is really not ideal.
I asked to be routed on IB via MAD (there are lots of options for sale on IB), and was told it’s not an option.
Any ideas why that’s the case? Should I try again?
thanks!