I've also had problem with mobile data, but after recreating APN and restarting phone IT works. After recreating APN mobile data worked after about 15 minutes. Check if everything with APN is ok, I've changed APN type in the end for default one.
Device Build Fingerprints: HUAWEI/MHA-L29/HWMHA:8.0.0/HUAWEIMHA-L29/373(C636):user/release-keys
Postscript This fingerpirint comes from LineageOS Beta 4 open kinrin.