Same issue here. In our case the Isilon device was upgraded and suddenly reported itself as machine type Fraunhofer FOKUS. The OID changed as a result of the upgrade.
Machine Type Isilon
Machine Type Fraunhofer FOKUS
I saw in another article where SRM was receiving and error that caused the issue but we do not currently utilize SRM.
I would think EMC would need to put out a patch for this.
Yes! We are currently having this same exact issue! Updated to 18.104.22.168 on our EMC Isilon's and both are showing as unreachable in NPM. We have our arrays added in via SRM. SRM test's the connection and shows everything as fine, but then lists it as unreachable. Extremely odd. I did also notice we now have a "Fraunhofer FOKUS" device as well.
Edit: Found this when I scrolled deeper in my thread search. Re: Isilon Devices No Longer Polling Following Upgrade to 22.214.171.124