After upgrading our Jenkins instance and plugins, the Perforce plugin can no longer access change logs and thus they don't show up in the web UI nor in other notifications.

Jenkins logs have the error message:

o.j.p.p4.changes.P4ChangeParser#parse: Could not parse Perforce changelog: <filepath>

Review of the perforce logs shows the following entries

Perforce server info:
    2023/06/28 16:23:26 pid 26543 jenkins.user@____CLIENT_UNSET____ JENKINSIP [jenkins.p4-plugin/1.14.1/Linux] 'user-login -s'
Perforce server info:
    2023/06/28 16:23:26 pid 26543 completed .014s 1+0us 0+0io 0+0net 8992k 0pf
Perforce server info:
    2023/06/28 16:23:26 pid 26544 jenkins.user@____CLIENT_UNSET____ JENKINSIP [jenkins.p4-plugin/1.14.1/Linux] 'user-property -nP4.Swarm.URL -l'
Perforce server info:
    2023/06/28 16:23:26 pid 26544 completed .006s 0+0us 0+0io 0+0net 8996k 0pf
Perforce server info:
    2023/06/28 16:23:26 pid 26544 jenkins.user@____CLIENT_UNSET____ JENKINSIP [jenkins.p4-plugin/1.14.1/Linux] 'user-property -nP4.Swarm.URL -l'
— failed authentication check

This was narrowed down to a problem introduced in version 1.12.1 and this change:

https://swarm.workshop.perforce.com/changes/28526

Adding back the isLogin check to a local build of plugin 1.14.1 resolves the issue.