Have you tried installing dbplyr as well? I can't remember at what version, but at some point the database connection functionality was removed from dplyr to the dbplyr package.
if I run
con1 <- src_postgres(host = "xx.xx.188.xxx", user = "myname", password = "mypassword", dbname="mydb")
with dplyr library version of 0.7.4, the below error will occur:
Error: Condition message must be a string
I think you will find the answer to the issue you are seeing here:
For future reference please, as @mara asked, post your code in the form of a reprex. It makes it much easier for us to help you. As is we have no idea what context your code was run in. If you include a reprex in your question we can run your code in the same environment as you do.
Whenever you get an error message that isn't clear about what is wrong the first thing you should do is do a web search for the message, for example search for "Error: Condition message must be a string". You might have to add extra qualifiers if the message isn't enough to zero in on your issue, for example adding dplyr to your search.
BTW if you every get an error message that is clear about what is wrong please let us and the whole world know