Ploltly is not showing in the hover all the variables used in aes().
Missing hover info with geom_rect:
library(ggplot2)
library(plotly)
test <- data.frame(C1 = c(2, 3), C2 = c(3, 4), C3 = c(2, 3), C4 = c(1, 4), C5 = c('A', 'B'))
ggplotly( ggplot(data=test) + geom_rect(aes(xmin=C1, xmax=C2, ymin=C3, ymax=C4, fill=C5)))
Result:

Complete hover info with geom_segment:
ggplotly(ggplot(data=test) + geom_segment(aes(x=C1, xend=C2, y=C3, yend=C4, color=C5)))
Result:
