Eurostar is currently full for days and weeks. You can check availability of the trains for Pass users here: Pass fare Thalys and Eurostar | SNCB International (b-europe.com)

Check also Paris-London or Lille-London. 

Hi, don’t know what you mean by “I have a travel”, but if you have no reservation yet, the first one available on this route is in the evening of the 20th (from Paris in the evening of the 19th). 

I have a travel it's that i activate that travel in my pass. Okey, so in seat obligatory I can't go without a seat? They are chances to new seats came out or it not use to happen?

All trains to London on 18 July are fully booked. There will not be any more available.

You need to find an alternative option.

No chance. If seats are free, you have to pay full ticket price. For Pass users only a quota of seats are available. 

AND expect strikes again to hit British trains in coming weeks-in case you find ALT ways.

ALT are-do we really have to tell? BUS-flix or Fly. The old style route train-ferry-train will not work for now via Calais-Dover, as these ferries do not take peoples without car/bike/motosy.

You may also have noted: there is a giant travelboom after covid--rules fell and staff shortages anywhere in transport mean fewer trains/buses/planes and also much longer time to pass checks etc. HOtel prices have also skyrocketed high lately