The logs showed that everything is working fine.
1) Viewer is plugin appropriately initialized. So viewer is downloaded.
2) WADO query is also OKIE
3) Weasis manifest file is also created.
4) Series are loaded
There is a connection error as indicated in the logs. If possible can you share the logs for review.
I would recommend that instead of using native viewer call why don't you shift to newer one. I am hopeful that it would solve your problem.
Otherwise, did you try to create the manifest file manually and check; were you able to view study or not????