PKP PLN plugin not enabled

With PKP’s help, our system is now 2.4.8.

The PKP PLN plugin is there with version.xml showing "version>
pln
plugins.generic
1.2.0.0
2015-07-13

I tried to “Enable” PKP PLN plugin for one journal. It gives no response. So I assume that something is not totally working. What are the things supposed to be happened after I click “Enable” link? Anywhere to check the problems?

(I assume it will ask to agree with the PLN preservation journal requirements at https://pkp.sfu.ca/pkp-lockss/#joining )

I installed Archive_Tar PHP and enabled CURL support. It is working now.