Fitting two coefplot in one graph using par(mfrow()) method

Question

I'm trying to arrange two coefplot objects into one graph via the par(mfrow(,)) method, but it didn't work out. What did I do wrong? Or is that coefplot just doesn't work this way? What will be alternative method? I've referenced this earlier thread, but I tend to think that mine is a quite different issue.

# load the data
dat <- readRDS(url("https://www.dropbox.com/s/88h7hmiroalx3de/act.rds?dl=1"))


#fit two models
library(lmer4)

act1.fit <- glmer(act1 ~ os + education + marital + nat6 + nat5 + nat4 + nat3 + nat2 + nat1 + 
    (1 | region_id), data = action, family = binomial, control = glmerControl(optimizer = "bobyqa"),
    nAGQ = 10)
    
action2.fit <- glmer(act2 ~ os + education + marital + nat6 + nat5 + nat4 + nat3 + nat2 + nat1 + 
    (1 | region_id), data = action, family = binomial, control = glmerControl(optimizer = "bobyqa"),
    nAGQ = 10)
    

# plot the two model individually
library(coefplot)

# construct coefplot objects

coefplot:::buildModelCI(action1.fit)
         
coefplot:::buildModelCI(action2.fit)
coefplot(action2.fit, coefficients=c("nat1", "nat2", "nat3", "nat4", "nat5", "nat6"), 
         intercept = FALSE, color = "brown3")
         
# arrange two plots in one graph
par(mfrow=c(1,2))
coefplot(action1.fit, coefficients=c("nat1", "nat2", "nat3", "nat4", "nat5", "nat6"), 
         intercept = FALSE, color = "brown3")
         
coefplot(action2.fit, coefficients=c("nat1", "nat2", "nat3", "nat4", "nat5", "nat6"), 
         intercept = FALSE, color = "brown3")         

# didn't work ???