Thanks for tips Sokaku :-)
Creating a new character showed that the tag at homebase was PlainsEdge, not Plainsedge. Changing the tag solved the portal issue. Next time I will build an untagged portal at homebase before exploring.
About the nails, I will try the tip using ladders if this happens again in the future. In my present location, I was lucky to find a burial cave close by with 10 surtling cores, so I built a charcoal kiln and a smelter, and then a forge to make new bronze nails.