Subject Re: [firebird-support] Firebird 3.0 client does not work with remote Firebird 2.5 database
Again email posts are not appearing here :(

Just twigged of-list that *I* have the same setup as Michael, but my first fix was exactly what Michael is trying to do. I could not connect to the local FB3 server, so I simply switched over so Local PHP was accessing the backup FB2.5 server on another machine. At that point I had not changed anything in the FB3 end and it all just worked. I only needed to change the FB3 settings to gain access to the FB3 server from an FB2.5 based Flamerobin and from the local PHP7.2 ...

So I suspect something not related to Firebird is in play here? Although the remote service Michael is accessing has been working previously and has not been changed, so it must be at the FB3 end that has the problem.