I am having problems selling certain goods , for example robots . Even offered them for two ages down
OThe Age/Era you're in, how many friends you have and how many if any guildmates you have will makeup and determine your market. If you are in Iron Age(IA) all your neighbors will be in IA, so there's potentially 25% of your market most likely not looking for Robotsa Contemporary Era (CE) good. You can only control the makeup of your market to some extent, mainly by choosing friends within the good Age/Era that you want to trade. So if you want to trade CE goods it's best to get friends in CE and above a few Eras. Choosing a large guild with a variety of players from Oceanic Future(OF) on down to Bronze Age(BA) is also good. And being in the Age/Era you want to trade in helps as well.
It's also important to understand some dynamics and paying attention to the metagame. For a long time a lot of players sat in Arctic Future(AF) and as such their Goods Great Buildings produced a lot of CE goods so demand for such will be lower. With OF opening up earlier this year there is now more demand for AF goods though as apparently many people mismanaged their goods and didn't build up and save AF goods and Promethium for OF.
One thing that can also help in trading is through guild hopping. Simply leave your guild and join others until you are satisfied with your trades. It's important to remember a couple things when doing this, one is you can't rejoin a guild for seven days after leaving and two, different guilds have different trade standards. Often guilds will label these trade standards as "fair trade" which means nothing but whatever they think it means, just be sure to be a good goods merchant and familiarize yourself with each guilds trading standard and trade with them in such a fashion as they require, this will ensure better future trade relations.
A couple other things you can do is have a guild message thread to announce trades your guildmates need. And you can also announce in Global Chat that you're looking to trade a certain good and see if anyone responds, you'll have to be friends, mates or neighbors with them to trade.