OQGraph doesn't produce next step links

Hi, I'm prototyping an accounting system based around OQGraph but I've hit a stop

Here's my data:
simple select on my graph table:
latch, origid, destid, weight, seq, linkid
,0,1,1,,
,1,2,1,,
,2,3,1,,
,3,4,1,,
,4,5,1,,
,4,6,1,,
,2,7,1,,
,7,8,1,,
,8,9,1,,
,7,10,1,,
,10,11,1,,
,1,12,1,,
,12,13,1,,
,13,14,1,,
,13,15,1,,
,12,16,1,,
,16,17,1,,
,16,18,1,,
,16,19,1,,
,16,20,1,,
,16,21,1,,
,16,22,1,,

SELECT linkid
FROM sa_coa_graph
WHERE latch = '1'
AND linkid > 0
AND destid = 22;

gives me

linkid
1
12
16
22

which is expected and works. Perfect for updating all the parent accounts in one go.

but

select linkid from sa_coa_graph where latch = ''
and origid = 0;

gives nothing. Not what I'm expecting. In this case I'd expect a result containing linkid == 1 i.e. the first hop link. Setting origid to any other 'parent' gives no first hop links as described in docs at https://mariadb.com/kb/en/library/oqgraph-examples/

In this case I want to use OQGraph to help me reconstruct the tree back into my parent program (PHP).As there is no functionality to get the linkage in any form of tree, I assumed you'd intended that this mechanism was a step towards doing so.

Am I missing something?

Kind regards