possible but not likely:  your friendly WIN Firewall blocks port 1972 in both directions)

#1
Caché Studio can't access IRIS for version reasons. Reverse IRIS studio can sometimes.
Better run separate versions.
#2
Studio requires access to SuperServerPort.  Actual 1972 previous was 51773.
if your IRIS runs in a Docker Container check the port mapping .    

Big THANKS to the whole community for the interest and the trust in my contribution,
Not to forget to thank the excellent support team and the fruitful cooperation within the community!

  GREAT !  covers all situations.

this works unlimited but has no exit if none unmatched found
method length = 64,
and it shows only the abs. value  38 instead of -38

s y=$lfs(o) f i=1:1 s a=$lf(y,i),b=$lf(y,-i) ret:a+b&'(a*b) i

but it  fails if the unpaired is < -9 as in the ref.example

"-110,110,-38,-38,-62,62,-38,-38,-38"    and doesn't stop

NICE.  but runs forever if there is no unpared. 
And why starting with  -9 ?

size = 65   return 0 if all pared;   { 0 is excluded for pairing }

ClassMethod Solve(o As %String) As %Integer
{
 s y=$lfs(o) f i=1:1:$ll(y) s c=$li(y,i) ret:'$lf(y,-c) c
 q 0
}

and you get 0 if numbers are paired !

Special thanks for defining the clear rules and excluding 'dirty' tricks  

Welcome on board !

example:

set def=##class(%Dictionary.CompiledClass).%OpenId("oex.Dir")
write def.SqlSchemaName
oex
write def.SqlTableName
Dir