I would suggest you update your version of RStudio.
I have tried this with RStudio version 4.0.3 and it worked fine.
library(sunburstR)
sequences <- read.csv( system.file("examples/visit-sequences.csv",
package="sunburstR") ,
header=F ,
stringsAsFactors = FALSE)
sunburst(sequences)
Default Sunburst
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…