Hello William 
From what I've seen, both ports 80 (http) and 443 (https) are closed for inbound connections to cnpd.pensions.rbm.mw. You can test this with:
Welcome to the Let's Encrypt Community, Myra
That will only check for outbound connectivity to the Let's Encrypt server. The problem here is that there is no inbound connection over port 80 for Let's Encrypt to reach cnpd.pensions.rbm.mw.