Error to load Power BI Custom Visual - DialGauge load error

Question

HI, I am working on Power BI report server May 2019 and have created Power BI report using custom visual Dial Gauge. When i publish the report to report server, the custom visual(Dial Gauge) does not show up. rest other visual are showing fine. while troubleshooting in browser console it was giving 401 unauthorized error for visual sandbox. error attached