I was able to create dashboards back in 8.1.9. After upgrading to 8.2.6, I get a weird error anytime I try to create a new dashboard or clone one (whether classic or studio). Haven't been able to find any information on it.
Figured it out after getting Splunk OnDemand Support. Our WAF in the F5 was blocking all the Rest API Calls. Once we had our network engineer make an exception to policy, the error went away. Can create/clone dashboards again.