Why application stopped to find library if it already exists

Question

Mono ASP.NET MVC 4.8 application uses wkhtmltopdf to create pdf file in Debian Linux.

wkhtmltopdf suddenly stopped working. Running it from shell throws library not found error:

root@x:/usr/local/bin# ./wkhtmltopdf
./wkhtmltopdf: error while loading shared libraries: libQt5Core.so.5: cannot open shared object file: No such file or directory

Symlink of library exists in /usr/lib/x86_64-linux-gnu :

root@x:/usr/lib/x86_64-linux-gnu# ls -l libQt5Core.so.5* 
lrwxrwxrwx 1 root root      20 jaan  30  2020 libQt5Core.so.5 ->
 libQt5Core.so.5.11.3 
lrwxrwxrwx 1 root root      20 jaan  30  2020
libQt5Core.so.5.11 -> libQt5Core.so.5.11.3
-rw-r--r-- 1 root root 5200168 jaan  30  2020 libQt5Core.so.5.11.3

How to allow wkhtmltopdf to find library in Debian Linux ?

I tried to copy library to the same directory where whhtmltopdf exists (/usr/local/bin ) but problem persists. It has worked for years but suddenly stopped working. Debian VPS server was re-booted unexpectedly, maybe this caused it.

Ran ldcongfig according to

Linux error while loading shared libraries: cannot open shared object file: No such file or directory

and tried

apt reinstall wkhtmltopdf
chmod 0777 /usr/lib/x86_64-linux-gnu/libQt5Core.so.5.11.3
LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/lib/x86_64-linux-gnu
export LD_LIBRARY_PATH
ldconfig
ldconfig -v | grep libQt5Core.so.5
echo $LD_LIBRARY_PATH
./wkhtmltopdf

but problem persists.

ldd returns:

:/usr/local/bin# ldd ./wkhtmltopdf
        linux-vdso.so.1 (0x00007ffff53a3000)
        libjpeg.so.62 => /usr/lib/x86_64-linux-gnu/libjpeg.so.62 (0x00007ff7d2c8f000)
        libpng16.so.16 => /usr/lib/x86_64-linux-gnu/libpng16.so.16 (0x00007ff7d2c56000)
        libXrender.so.1 => /usr/lib/x86_64-linux-gnu/libXrender.so.1 (0x00007ff7d2a4c000)
        libfontconfig.so.1 => /usr/lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007ff7d2a06000)
        libfreetype.so.6 => /usr/lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007ff7d294a000)
        libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007ff7d2738000)
        libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007ff7d25f5000)
        libssl.so.1.1 => /usr/lib/x86_64-linux-gnu/libssl.so.1.1 (0x00007ff7d2563000)
        libcrypto.so.1.1 => /usr/lib/x86_64-linux-gnu/libcrypto.so.1.1 (0x00007ff7d227a000)
        libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007ff7d205c000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007ff7d2057000)
        librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007ff7d204d000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007ff7d202a000)
        libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007ff7d1ea6000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007ff7d1d23000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007ff7d1d09000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ff7d1b48000)
        /lib64/ld-linux-x86-64.so.2 (0x00007ff7d5c28000)
        libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007ff7d1b0b000)
        libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007ff7d1b00000)
        libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007ff7d1ad6000)
        libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007ff7d18d2000)
        libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007ff7d16cc000)
        libbsd.so.0 => /usr/lib/x86_64-linux-gnu/libbsd.so.0 (0x00007ff7d16b2000)