I have a iPhone 8 and I pressed forget this on a Bluetooth device how do I reconnect with it ????? I’ve tried resetting network

You have to pair your iphone again with that BT accessory.

Read this support guide:

Pair a third-party Bluetooth accessory with your iPhone, iPad, or iPod touch - Apple Support

You might need to read also your accessory's user manual.

Regards

Giulio

Put the device back into pairing mode and just re-pair it.

Is the BT device itself in pairing/discoverable mode? Most devices will need to be reset to that if they have been previously paired to any device.

And the speaker is indicating it is discoverable? Mose BT devices in pairing mode indicate it by some kind of LED flash or color change.

Check the speaker's manual or search online on how to make the speaker "discoverable". It may take a specific button sequence or procedure.