An issue installing an extension

I have 3 machines that _should_ be nearly idnetical. On 2 of them, i have
no issues installing an extension I copiled. On one I get the followign
error message:

icadb=# CREATE EXTENSION IF NOT EXISTS pg_libphonenumber;
ERROR: could not load library
"/usr/lib/postgresql/11/lib/pg_libphonenumber.so": libphonenumber.so.7:
cannot open shared object file: No such file or directory
icadb=# ls -l /usr/lib/postgresql/11/lib/pg_libphonenumber.so

Yet,

root(at)ica-db:/home/stan/BUILD/pg-libphonenumber-master# ls -l /usr/lib/postgresql/11/lib/pg_libphonenumber.so
-rwxr-xr-x 1 root root 182976 Oct 22 16:11 /usr/lib/postgresql/11/lib/pg_libphonenumber.so

This appears to be identical to the other machines where this works,

root(at)smokey:/home/stan/BUILD/pg-libphonenumber-master# logout
stan(at)smokey:~/BUILD/pg-libphonenumber-master$ ls -l /usr/lib/postgresql/11/lib/pg_libphonenumber.so
-rwxr-xr-x 1 root root 182976 Oct 22 09:47 /usr/lib/postgresql/11/lib/pg_libphonenumber.so

What else could be wrong?

--
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
-- Benjamin Franklin