Try it again with a fresh brain (there’s an archive) but this time try start from the centre, moving outwards in a spiral, and apply symmetry on the diagonals e.g. repeat what you did top left on the bottom right, etc. If something gets blocked, undo a few steps and make the same change symmetrically.
That is the approach on my (4th?) attempt that finally worked for me.
Try it again with a fresh brain (there’s an archive) but this time try start from the centre, moving outwards in a spiral, and apply symmetry on the diagonals e.g. repeat what you did top left on the bottom right, etc. If something gets blocked, undo a few steps and make the same change symmetrically.
That is the approach on my (4th?) attempt that finally worked for me.