This can be caused by several issues. First, when copying the licence key string either from the email sent by Aculab or from the screen of the web-based licence server, make sure that extra spaces are not being appended to your key string.
Second, an incorrect machine ID can also cause install failures. The machine ID is a parameter used with Aculab's legacy licensing mechanism that ties a licence to a particular set of hardware, but its structure also includes a random number component. Each licence key installed onto a server will have a unique machine ID. When performing an upgrade to an existing licence, a new licence key is added to the target server. The new key MUST be generated using a new machine ID that is provided by the ACT or licenceAdmin command line tool on the target server.
Aculab's new style licensing mechanism does not require a Machine ID so the possibility of a bad Machine ID causing an install fail is eliminated. Note, however, that even without a Machine ID, the licence install has to be validated at installation time via connection back to Aculab's licensing servers.