Please help - issue in restoring WhatsApp chat - Support not replying

Hi - I understand there have been many threads about restoring chats but I think my situation is quite unique. I have emailed WhatsApp 4 times about it - 1st time got automated response but no reply when I questioned them on it, 3 other times I got no reply at all. Here it is:

I regularly backed up my WhatsApp chats onto Google Drive on my Samsung Galaxy S7 and did just as it was about to break. Once the screen broke I had to put my SIM into my old Xperia Z1 and use WhatsApp on there. I installed it and put in my phone number and logged into my Google Drive and restored chats. But somehow it was only showing chats from up to around a year ago on there - all my recent 2018 chats were gone - but somehow in my phones media gallery I could see restored WhatsApp pictures from chats in the last few weeks - but no chats to go with them on the app. I still would have backups done on the Z1 as I used this for about 2 weeks until I bought a Huawei P20 Pro.

I install WhatsApp on the P20 thinking this might be able to restore the recent 2018 chats I had backed up (told me I had about 700MB worth of chats backed up) but when I restored the chats I could only see the same ones from 2017 there. It didn't make any sense. And again the restoration put in photos from recent chats onto my images folder.

I can't do anything on my S7 until I get enough money to fix the screen again but I definitely was backing chats up to Google Drive - how can I get back the older 2018 chats? I desperately need some of them.

Thanks