The Zotero has changed the link style for items for several months. The old style works on Mac but fail in the iOS devices. I modified the Zotero script for temporary usage.
set firstChar to character 1 of theLink
set secondChar to character 2 of theLink
set firstDigit to (firstChar as integer)
set myLink to text 3 thru -1 of theLink
if secondChar is not "_" then
set theLink to "[" & theName & "](zotero://select/library/items/" & theLink & ")"
else if firstDigit is 1
set theLink to "[" & theName & "](zotero://select/library/items/" & myLink & ")"
else if firstDigit is 2
set theLink to "[" & theName & "](zotero://select/groups/[group1id]/items/" & myLink & ")"
else if firstDigit is 3
set theLink to "[" & theName & "](zotero://select/groups/[group2id]/items/" & myLink & ")"
else if firstDigit is 4
set theLink to "[" & theName & "](zotero://select/groups/[group3id]/items/" & myLink & ")"
end if
The [group1id] is the number for each groups.