Currently, the UniProt links are not seen in the curator tool for some entries. See for example EC 126.96.36.199. There are 5 entries linked (in ENZYME view) but not in IntEnz view.
I have found out that this happens when there are no other links specified, i.e. If there are no links specified OR there are only UniProt links, then NO LINKS are displayed in the tool.
If one link is specified e.g. diagram, or PROSITE link, then all links are displayed (BRENDA, UniProt, KEGG, etc).