The problem is not that he is not eating solids. He is young. At this age and for the 1st year, "solids" is only an introduction to foods... NOT the main staple.
For the 1st year of life... breastmilk or Formula is a baby's PRIMARY source of nutrition... NOT solids and NOT other liquids. Per our Pediatrician as well.
Continue to nurse him or give Formula if that is what you are doing, on-demand. ALWAYS nurse or give Formula, BEFORE solids.... otherwise, if you give solids 1st before nursing, a baby will 'wean' from breast. You do NOT want this to happen.
A baby, still needs, primarily, breastmilk or Formula... and on-demand.
6 months is also a growth-spurt time... so they naturally increase in nursing frequency and intake amounts.
CONCENTRATE on nursing him or giving Formula... whichever you are doing. On-demand. 24/7. And so that he does not get dehydrated.
A baby, does not need the baby "fruits." That is just sweet and sugar stuff. Primarily, solids should be minimal... NOT 3 times a day... and starting with cereal.... single grain cereal. Then after a few months, veggies either yellow or green veggies... etc.
Again, at this age, the priority should not be only solids nor 3 times a day nor in huge amounts. Otherwise, a baby will wean from breast or Formula. Right now and for the 1st year... breastmilk/Formula is still a primary thing and source of nutrients....
all the best,
Susan