hard to select 4wd

hi all. plz need your help.
i got a jimny 1999 manual gear hard top 1 year ago no modification at all yet in Lebanon (middle east). i used 4wd about 6 times last winter in a distance about 20 km only while on move in straight wheel i pushed the clutch pedal and switched from 2wd to 4wd at a speed between 30-70km/h with no problem engaging and disengaging on wet and dry surfaces. i didn't do any modification for hubs or lifting or differential or pipes etc... this winter i tried to use 4wd on normal wet road by pushing clutch pedal and straight wheel ,speed about 40 km/h. but the gearstick(lever) was hard to move from 2wd to 4wd high even i pushed many times clutch on neutral position speed or i let the RPM go little higher so i couldn't drive 4wd high. when i park near my home , i tried again to switch from 2wd to 4wd and it worked well and easily , i did that for 3 times engage and disengage normaly and each time listen click click on both wheels. when driving again also i couldn't use 4wd.
sorry for disturbing , i appreciate your suggestion. thanks

Why dont you just stop and put it in 4wd save damaging the tranfer box and front hubs

you are right. but i like that 4wd work normaly as it is new and like they say that u can switch from 2wd to 4wd high when driving up to 100km/h in jimny. here in Lebanon (middle east ) i think there is few jimny here maybe about 10 cars or maybe 20. all people here say that its not a well-known car and the company didnt bring a lot of that model here .so only in the company they fix jimny.and they dont let customer(me) see what they check. maybe they will say that i must change the hubs or the vacuum valve or something. i mean maybe they will change many things just to let me pay.u know companies steal money from customer. so i asked u cz maybe it's a small or known problem

i'm interseted ,i read a lot on this forum and registered .i am a new member .and its little bit hard for me to communicate or use that forum.

u all have experience in jimny and maybe someone had that problems before and get fixed
so i ask u guys cz in my country (Lebanon) jimny is not a well-known car even 3 kinds of scanner couldnt access my jimny. there is only 2 broken suzuki cars shop near me and told me that there is not a lot of jimny here. its hard to find spare parts. only from company i can buy original parts. but not accessories or body lifting kit or shock spacers or extra long springs for lifting or wind deflectors or LED headlights etc....... i mean only they have standard spare parts.
my jimny is still standard as it comes. i only put yokohama 195/80/15 and its good .
hope u can help me finding the problem. thanks in advance for all members and helpers

I only do it at low speed

you shouldnt be using 4wd on the road even if it is wet!!

you may have broken something in the driveline.

only use 4wd if the wheels can spin ie lose traction.