Picker not showing up in element-web

[jomat]

One of my users doesn't get the stickers working in element-web. He added the correct m.widgets json (see below), cleared cache and reloaded, logged out and back in to element-web, uses the same element-web instance as i do (so x-frame-options and similar should be ok), but just gets the bunny saying he hasn't enabled any packs. what else could we check?

synapse=# select * from account_data where user_id='@Redacted:asra.gr' and account_data_type='m.widgets';
        user_id        | account_data_type | stream_id |                                                                                                                                  content                                                                                                                                   | instance_name 
-----------------------+-------------------+-----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+---------------
 @Redacted:asra.gr | m.widgets         |   3535283 | {"type":"m.widgets","content":{"stickerpicker":{"content":{"type":"m.stickerpicker","url":"https://sticker.asra.gr/?theme=$theme","name":"Stickerpicker","data":{}},"sender":"@Redacted:asra.gr","state_key":"stickerpicker","type":"m.widget","id":"stickerpicker"}}} | 
(1 row)