Hi rlriales,
ERS API doesn't allow minus character in "Network Device Group" name bug has resolved in ISE 3.1 patch 5. Currently Cisco recommended ISE version is 3.1. Hence you can upgrade your ISE to version 3.1 patch 5. Kindly find the details in below URL. you can search the bug using bug id CSCwc65821
https://www.cisco.com/c/en/us/td/docs/security/ise/3-1/release_notes/b_ise_31_RN.html
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If you find my reply solved your question or issue, kindly click the 'Accept as Solution' button and vote it as helpful.
You can also learn more about ISE through our live Ask the Experts (ATXs) session. Check out the ATXs Resources [https://community.cisco.com/t5/security-knowledge-base/cisco-endpoint-security-ask-the-experts-resources/ta-p/4394492] to view the latest schedule for upcoming sessions, as well as the useful references, e.g. online guides, FAQs.
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Regards
Arunkumar
