When defining a connection to an Acumatica tenant whose name contains an Ampersand (&), one of the following error messages is displayed:

Text from the Error Message:

Internal server error (500). The server encountered an
internal error or misconfiguration and was unable to
complete your request.

or

Unexpected error while processing the response. Please
ensure that you can connect to Acumatica and that the site is
not under maintenance.

Certain versions of Acumatica return an error when an external product attempts to connect to a tenant whose name contains a "special" or "reserved" character such as

& < > * % : ; \ / ?

Within Acumatica, rename the tenant so that it does not include any special characters

e.g.,