in slow 4 the first outpost tech has reset. i now have expert outposts tech and can see 10 hexes despite having purchased prevoius techs. The first outpost tech is available to buy again.

only thing i did was sell one of my original outposts.

Perhaps you sold/removed the outpost that you purchased the upgrade on, if so, that's why the outposts have returned to their original 'seeing' distance.

You mean he build the outpost before the upgrade that changed them to a tech?.

you might be right. thiwas in progress when the new rule changes took effect. is this a rule or a glitch cause by the rule change mid game

Yep, before when the additional range was an Upgrade, you decided which outpost to purchase the upgrade on...now, we all knew a bug 'gave' ALL outposts the additional vision, but if you removed the outpost that you had purchased the upgrade on, you lost the upgrade on ALL outposts.
Now, since the improved line of sight is a tech, that problem should be resolved.