That happened to me last year. I sowed a raised bed with chard which didn't germinate. I wondered if it was because the bed had been filled with goat manure so I had several bags of compost spread over it and sowed another lot.
After three weeks of nothing, I was in the garden centre and saw they had chard seedlings for sale so I bought three little trays - about 36 plants. Went to plant them the next day and found all the seeds had germinated. I had to go and buy more compost to fill various troughs and pots to take all the seedlings.
We had plenty of chard to eat last year and the stuff in pots is still doing well