Spyder: variable explorer does not show variable for connected remote kernel

Spyder variable explorer works fine for a local kernel; however, it does not work for the remote kernel. Indeed, the connection to the kernel and running the codes works well but non of the variables are shown in the varibale explorer.

Here is some information:

Python 3.6.8 64-bit | Qt 5.9.4 | PyQt5 5.9.2 | Linux 4.9.0-6-amd64

I also unmarked all filters in "Preferences>Variable explorer>Filter" and followed the posts below but no improvement.

https://github.com/spyder-ide/spyder/issues/7850

Spyder does not show lists and arrays in variable explorer

• spyder-kernels is installed in both local and remote machines.
• the connection is through SSH.
• Spyder is up to date.

Thanks in advance for your helps.