I ran through the tutorial and didn't get the same issue that you are having when I ran myContract.increment()
Suggest you check the address that you specified in truffle console:
https://docs.zeppelinos.org/docs/upgrading.html
Make sure you replace with the address of the upgradeable instance your created ofMyContract. This address was returned by thecreatecommand we ran in the previous section, which is the same as the one returned by theupdatecommand we ran above.
truffle(local)> myContract = await MyContract.at('<your-contract-address>')
Also when you setup the session, use a ganache account which isn't the first one.
How to create an upgradeable smart contract using ZeppelinOS — example of fixing smart contract vulnerable to underflow/overflow attacks
npx zos session --network local --from 0x9ea26a91A3eF090498827989d17FC0E7eEA0987f --expires 3600
Remember to replace the address after--fromflag with one of your Ganache accounts, but do not use the first one (account[0]). I usually choose the second (accounts[1]) or the last one (accounts[9]). You should also use network specified in your truffle-config.js (in our case it is local ).