CMN_SEC_USERS_PK is a unique constraint check on CMN_SEC_USERS.ID (the primary key), so you've managed to get the primary key generator out of sync.
Most commonly, I see this happen when a database backup is taken (whilst the application is still running) and then this backup is used in another environment (in order to perform a test upgrade, for example). What happens is the primary key generator (sequence) is one of the first things to be backed up, then it reaches the tables by which time more data has already been inserted. So you end up with (for example) the backup thinking the sequence is currently on user 5000010, but the table is now up to 5000034 and the next ~24 users are all going to fail.
To solve, run these queries to first confirm:
select max(id) from cmn_sec_users
select cmn_sec_users_s1.nextval from dual
If the first result is higher than the second, then you have a sync problem.
To correct, find the difference between the two numbers and round up to the nearest thousand (to be safe). Say the value happens to be 6000. You would then run the following on your DB:
alter sequence cmn_sec_users_s1 increment by 6000
select cmn_sec_users_s1.nextval from dual
alter sequence cmn_sec_users_s1 increment by 1
select cmn_sec_users_s1.nextval from dual
(Note: all 4 queries are important, even though one of them is repeated twice, as it actually invokes the sequence incrementer code to move the value along).
This applies on Oracle, where the backup/restore is done using exp/imp, and the constraint in question is on the table's primary key.
That's all fine and good if only a sequence or two are out of sync, otherwise I would instead suggest redoing the backup and restore of the DB, either from a time when there is a maintenance window and the Clarity services are stopped, or by changing the method of the backup may be sufficient. Making use of Oracle's newer import/export capability called Datapump (e.g. expdp/impdp) would likely avoid this, as it is better at handling database consistency by default, and I rarely see a problem like this.
Otherwise you may be in for a painful hit-and-miss of one sequence after the other failing during the upgrade and/or afterwards when trying to use or test it.