Tree preservation zone

There is a problem

tree-preservation-order column must match the reference field in the tree preservation order dataset

reference: 33-A2
name: East Hertfordshire District Council (Chells Manor, Stevenage) Tree Preservation Order (No. 6) 1985
tree-preservation-order: undefined
33
tree-preservation-zone-type: group
geometry: MULTIPOLYGON (((-0.157847 51.906209,-0.157917 51.906264,-0.158102 51.906604,-0.158173 51.906768,-0.158220 51.906975,-0.158199 51.907066,-0.158164 51.907133,-0.158160 51.907235,-0.158184 51.907346,-0.158178 51.907433,-0.158218 51.907571,-0.158253 51.907715,-0.158316 51.907805,-0.158393 51.907888,-0.158488 51.907963,-0.158625 51.908058,-0.159014 51.908299,-0.159342 51.908529,-0.159465 51.908622,-0.159633 51.908753,-0.159799 51.908858,-0.160077 51.909040,-0.160170 51.909103,-0.160337 51.909168,-0.160632 51.909294,-0.160798 51.909335,-0.161011 51.909399,-0.161379 51.909521,-0.161503 51.909587,-0.161621 51.909666,-0.161723 51.909776,-0.161835 51.909780,-0.161773 51.909688,-0.161709 51.909637,-0.161440 51.909490,-0.160897 51.909314,-0.160652 51.909239,-0.160459 51.909161,-0.160156 51.909008,-0.159624 51.908680,-0.159445 51.908547,-0.159199 51.908343,-0.159073 51.908268,-0.158637 51.907985,-0.158449 51.907855,-0.158336 51.907721,-0.158302 51.907646,-0.158231 51.907332,-0.158263 51.907121,-0.158299 51.907019,-0.158276 51.906875,-0.158232 51.906685,-0.158176 51.906564,-0.157967 51.906090,-0.157847 51.906209)))
point: POINT (-0.159301 51.908091)
notes: Lanterns Lane Stevenage Herts
entry-date: 1985-09-17
start-date: 1985-09-17
end-date

Your data is missing a tree-preservation-order.

The Tree preservation zone guidance explains how to fix the issue:

The reference for the tree preservation order that covers this zone.