R workspace keep empty when used in VScode

I tried to build R environment in VScode. But the workspace region still showed nothing when I created R dataframe.

What I've done:
I created a r_env environment on Linux server for R analysis. I've installed R packages including httpgd, languageserver and radian. The versions are as below:
r-base 4.4.3 h9c32bc2_0 conda-forge
r-httpgd 2.0.4 r44h93ab643_0 conda-forge
radian 0.6.13 pypi_0 pypi
packageVersion('languageserver')
[1] ‘0.3.16’

My settings.json is as below:
{
"r.alwaysUseActiveTerminal": true,
"r.bracketedPaste": true,
"r.rterm.option": [
"--r-binary=/mnt/data/userdata/zhangliyin/anaconda3/envs/r_env/bin/R",
"--no-site-file"
],
"r.plot.useHttpgd": true,
"r.rterm.linux": "/mnt/data/userdata/zhangliyin/anaconda3/envs/r_env/bin/radian",
"r.rpath.linux": "/mnt/data/userdata/zhangliyin/anaconda3/envs/r_env/bin/R",
"r.workspaceViewer.removeHiddenItems": true,
"r.workspaceViewer.showObjectSize": true
}

I read some of similar issues and tried mentioned solutions, but the problem still remains. I would really appreciate your help! Thanks a lot!

Reproduce the empty workspace region using the provided settings.json, R environment, and dataframe example. Start by checking whether the R workspace viewer receives objects when r.workspaceViewer.removeHiddenItems and r.workspaceViewer.showObjectSize are enabled. Done means the created dataframe appears in the VS Code workspace viewer, with the relevant setup behavior documented.