I have the same issue, 500 Internal Server Error, regardless of the version being used (I updated to 0.6.11 with little hope it would change anything). On Playmaker 1.9.0p21, Unity 2019.4.23.
WARNING
Search Error : The remote server returned an error: (500) Internal Server Error.
UnityEngine.Debug:LogWarning (object)
Net.FabreJean.PlayMaker.Ecosystem.EcosystemBrowser:OnInspectorUpdate () (at Assets/net.fabrejean/Editor/PlayMaker/Ecosystem/EcosystemBrowser.cs:2422)
UnityEditor.HostView:OnInspectorUpdate () (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:270)
INFO
ParseSearchResult
UnityEngine.Debug:Log (object)
Net.FabreJean.PlayMaker.Ecosystem.EcosystemBrowser:ParseSearchResult (string) (at Assets/net.fabrejean/Editor/PlayMaker/Ecosystem/EcosystemBrowser.cs:2485)
Net.FabreJean.PlayMaker.Ecosystem.EcosystemBrowser:OnInspectorUpdate () (at Assets/net.fabrejean/Editor/PlayMaker/Ecosystem/EcosystemBrowser.cs:2438)
UnityEditor.HostView:OnInspectorUpdate () (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:270)
WARNING
Json parsing error Object reference not set to an instance of an object
UnityEngine.Debug:LogWarning (object)
Net.FabreJean.PlayMaker.Ecosystem.EcosystemBrowser:ParseSearchResult (string) (at Assets/net.fabrejean/Editor/PlayMaker/Ecosystem/EcosystemBrowser.cs:2515)
Net.FabreJean.PlayMaker.Ecosystem.EcosystemBrowser:OnInspectorUpdate () (at Assets/net.fabrejean/Editor/PlayMaker/Ecosystem/EcosystemBrowser.cs:2438)
UnityEditor.HostView:OnInspectorUpdate () (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:270)
INFO
UnityEngine.Debug:Log (object)
Net.FabreJean.PlayMaker.Ecosystem.EcosystemBrowser:ParseSearchResult (string) (at Assets/net.fabrejean/Editor/PlayMaker/Ecosystem/EcosystemBrowser.cs:2516)
Net.FabreJean.PlayMaker.Ecosystem.EcosystemBrowser:OnInspectorUpdate () (at Assets/net.fabrejean/Editor/PlayMaker/Ecosystem/EcosystemBrowser.cs:2438)
UnityEditor.HostView:OnInspectorUpdate () (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:270)
Also—and that's a long term grief I have about the Ecosystem UI—the text, buttons, sliders and search field are very hard to see in the default black nightmode interface. I might understand the love some nurture for everything related to caves, death, gloom and despair, but surely a little but of improvement on the UX front would be welcomed.
I'd also think a lightmode would be nice too.