Marshall Bluetooth Speaker connected on bluetooth but sound still from iPhone

hi

It seems this has been mentioned numerous times but I can't find any clear answer for my case

Basically:

• the device is connected on bluetooth to the phone (I can see it on the speaker's app on my phone as well as on the bluetooth settings)
• when I play music it doesn't go to the speaker, it plays on the phone
• when i look at the devices available in the "pull up menu" (the one you drag up from the bottom of the screen) I can't see my speaker in my list of sound devices
• I have the latest iOS (13.4)
• I reconnected, reconnected , switched on/off plenty of times it doesn't change anything
• It was working fine on my previous iPhone 7 (apple exchanged it to a new iPhone 7 as the previous one had a defect)

It's like it doesn't recognise the speaker as a sound device

Very annoying, was working fine on old phone, get it replaced by same model new one and now it does't work..

Any help welcomed!

Thanks