The login credentials are correct. I tried this plugin with another theme on a different site, same credentials, and it worked fine.
Looks like if I open the post and switch to Advanced Editor and then save it again the excerpt will display. This seems rather strange and I don’t know if it’s a glitch with the theme. For now I’ll have to insert posts via Advanced Editor but if someone could check this I would appreciate it. I don’t use the Advanced Editor and normally just use the Text view. Thanks!