problem with A1-810 Acer tab, please help

Sakama

I have this tab long time, and I never update anything there. Because of very slow browser I decide to update my system. But there was a problem, Acer community shut down that option and I can update my system only manually. Ok, I debug USB in settings and using SD card tried to update new system. I found isystem on Acer web page. But instalation aborted and I can't use my tab anymore,  there was no any system because new instalation delited old system. I tried many time to update new system but no results, with every instalation packagr I have same result: 
-- Install /sdcard ...
check.partition.size=[__PROP_UNDEFINED__]
installation aborted.

Can anyone help me with some advice or link. I'm not profesional with computers and programs but I can lean a lot. I lost three days on this but no result, I can't do it alone.

Thanks a lot

Sakama

Sakama said:

I have this tab long time, and I never update anything there. Because of very slow browser I decide to update my system. But there was a problem, Acer community shut down that option and I can update my system only manually. Ok, I debug USB in settings and using SD card tried to update new system. I found isystem on Acer web page. But instalation aborted and I can't use my tab anymore,  there was no any system because new instalation delited old system. I tried many time to update new system but no results, with every instalation package I have same result: 
-- Install /sdcard ...
check.partition.size=[__PROP_UNDEFINED__]
installation aborted.

Can anyone help me with some advice or link. I'm not profesional with computers and programs but I can lean a lot. I lost three days on this but no result, I can't do it alone. One more problem, my computer can't connect with my tab using usb cable, computer can't detect my acer A1-810.

Thanks a lot