Error when trying to add imei

I get this error in traccar server gui when i try to add a unit wit the imei "352887076539562"

Unique index or primary key violation: "UK_DEVICE_UNIQUEID_INDEX_B ON PUBLIC.DEVICES(UNIQUEID) VALUES ('352887076539562', 9)"; SQL statement:
INSERT INTO devices (model, category, name, groupId, uniqueId, attributes, contact, lastUpdate, phone) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?) [23505-196] - JdbcSQLException (... < QueryBuilder:477 < DataManager:455 < BaseObjectManager:87 < ...) 

Running the latest traccar server traccar-other-3.14.zip

In my tracker-server.log i see the id: 352887076539562

2017-10-12 22:37:31 DEBUG: [5C1E5EDB: 5023 < 95.195.203.188] HEX: 78780d01035288707653956200056c630d0a
2017-10-12 22:37:31 DEBUG: [5C1E5EDB: 5023 > 95.195.203.188] HEX: 787805010001d9dc0d0a
2017-10-12 22:37:34 DEBUG: [5C1E5EDB: 5023 < 95.195.203.188] HEX: 78780a1300050402010006bb740d0a
2017-10-12 22:37:34 DEBUG: [5C1E5EDB: 5023 > 95.195.203.188] HEX: 787805130002db6a0d0a
2017-10-12 22:37:36  INFO: [5C1E5EDB] id: 352887076539562, time: 2017-10-12 18:21:38, lat: 60.14434, lon: 16.17104, speed: 0.0, course: 0.0
2017-10-12 22:37:37 DEBUG: [5C1E5EDB: 5023 < 95.195.203.188] HEX: 78781f12040101000029c00673ea7601bc1f7100040000f00109df00dc3e00071c6c0d0a
2017-10-12 22:37:37 DEBUG: [5C1E5EDB: 5023 > 95.195.203.188] HEX: 787805120003903f0d0a
2017-10-12 22:37:37  INFO: [5C1E5EDB] id: 352887076539562, time: 2004-01-01 01:00:41, lat: 60.14442, lon: 16.17002, speed: 0.0, course: 0.0
2017-10-12 22:37:40 DEBUG: [5C1E5EDB: 5023 < 95.195.203.188] HEX: 78781f12110a0c11321ac80673e99201bc20a800140000f00109df00dc3e0079d6e50d0a
2017-10-12 22:37:40 DEBUG: [5C1E5EDB: 5023 > 95.195.203.188] HEX: 787805120004e4800d0a

But i cant add that id in the gui.

It means that you have already added it, possibly to another user.