problem with serial

i do have a serial named 'rowid' it is of "SERIAL PRIMARY KEY" in a table 'items'.

if i delete some of the rows i can't anymore insert afterwards.

even if i rearrange de sequence by :

"SELECT MAX(rowid) FROM items;";
"SELECT last_value FROM items_rowid_seq;";
then if last_value is lower than MAX(rowid) i set it to MAX(rowid) :
"SELECT setval('items_rowid_seq', max(rowid)) FROM items;";

and even after that i get an error when inserting by :
"INSERT ... RETURNING rowid;"

here I'm not only unable to read back the rowid but also inserion failed.

why ?
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