I previously 'installed' WinPython 3.7.7.0 (x64) to a path resulting in
"C:\Program files (portable)\WinPy_3-7\WPy64-3770\Spyder.exe"
and also WinPython 3.8.3.0-RC (x64) to a path resulting in
"C:\Program files (portable)\WinPy_3-8\WPy64-3830\Spyder.exe"
Each of these ran with no problem. The OS is Windows 10 Pro for Workstations (x64).

On a different workstation, following the same procedure, I 'installed' 3.8.9.0 (x64) to a path resulting in
"C:\Program files (portable)\WinPy_3-8\WPy64-3890\Spyder.exe"
and also WinPython 3.9.5.0 (x64) to a path resulting in
"C:\Program files (portable)\WinPy_3-9\WPy64-3950\Spyder.exe"
NEITHER of these ran at all. The OS is Windows 10 Pro for Workstations (x64) too.
Running Spyder produced nothing, including no error message. However, running "Jupyter Lab.exe" from the above two directories indicated a problem with the path name, with the following error message reported in the 'console' (cmd window):
"\WinPy_3-9\WPy64-3950\scripts was unexpected at this time."
Notice that this comprises the path immediately after the closing parenthesis, ")".

On the second workstation I tried copying the files to "c:\TMP". They all ran just fine.
I also tried "C:\TMP 0123456789_ A0123456789_ B0123456789_ 0123456789_" to check issues with a long pathname or spaces. All executables ran just fine.
Even with an opening parenthesis in the path there is no problem.
The problem only occurred with a closing parenthesis in the path (regardless of the presence or absence of an opening parenthesis).

—DIV

P.S. Each 'installation' is a portable installation, without 'registration'. One was manually extracted using an installed copy of 7-Zip. The remainder all used the self-extraction capability of the 'installer'.