Internet goes out multiple times and no technician can fix it

i’ve had 5 technicians come out and none have been able to solve my issue. after 4 o’clock every day my internet comes in and out and no technician can seem to find the fix for it. i’ve had my line and modems replaced twice now and the haven’t fixed the issue. why can’t they fix it? what good are the technicians for then? I NEED ACTUAL HELP. IM VERY FRUSTRATED!