All string fields are case sensitive. Even if the item is showing as upper case in game, it may not be upper case. Assess what the true case nature of the displayName is and update it appropriately.
Alternatively, make it based on the skin id if applicable.
I am updating this in the next release though.
The new logic will work like so:
If the blacklist skin is > 0, it will assess to see if the skin is a match.
If the shortname of the blacklist is not null or empty, it will check to see if the item shortname is a match.
If the displayName of the blacklist is not null or empty, it will check to see if the item displayName is a match. It also has the option for partial name checks, so you can use shorter names to capture more items, such as "bag" would match with "bag of holding" and "enchanted bag".
If the text field of the blacklist is non-null or empty, it will function the same way as the displayName, including a partial search option for text.
An example of what this looks like.
This prevents ANY bag from being added.
{
"shortname": "largebackpack",
"skin": 0,
"displayName": null,
"partialNameAccepted": false,
"text": null,
"partialTextAccepted": false
},
This would prevent only the bag with the matching names from being added (case sensitive).
{
"shortname": "largebackpack",
"skin": 0,
"displayName": "enchanted",
"partialNameAccepted": false,
"text": null,
"partialTextAccepted": false
},