ref: Loading pgAdmin 4 v7.4... while opening pgAdmin
I had the same problem when installing pgAdmin via the postgresql-15.3-3-windows-x64 installer.
Solution:
- uninstall PostgreSQL;
- reinstall PostgreSQL but in the components selection, uncheck PG Admin;
- download pgAdmin from https://www.pgadmin.org/download/ and install it.
Above is the answer from the website. For my case, I didn't uninstall PostgreSQL. I downloaded the pgAdmin and installed it directly. And now it works well.