subscription broken after upgrade to pg11

Hi All,
We're testing upgrade from postgres 10.6 to postgres 11.2 with pg_upgrade.
Before stopping pg10 we disabled subscription.
After upgrade and launching pg11, the existing logical replication
subscription is there and disabled.

stest=# \dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Synchronous commit |
Conninfo
------+----------+---------+-------------+--------------------+-----------------------------------------
sub1 | postgres | f | {pub2} | off |
host=10.2.5.8 dbname=test user=postgres
(1 row)

However after enabling it, the target table does not get updates,
although the subscription looks okay according to the status below.

stest=# alter subscription sub1 enable;
ALTER SUBSCRIPTION
# no updates here

stest=# \dRs+
List of subscriptions
Name | Owner | Enabled | Publication | Synchronous commit |
Conninfo
------+----------+---------+-------------+--------------------+-----------------------------------------
sub1 | postgres | t | {pub2} | off |
host=10.2.5.8 dbname=test user=postgres

stest=# select * from pg_subscription;
subdbid | subname | subowner | subenabled | subconninfo
| subslotname | subsynccommit | subpublications
---------+---------+----------+------------+-----------------------------------------+-------------+---------------+-----------------
16402 | sub1 | 10 | t | host=10.2.5.8 dbname=test
user=postgres | sub1 | off | {pub2}

stest=# select * from pg_stat_subscription;
subid | subname | pid | relid | received_lsn | last_msg_send_time |
last_msg_receipt_time | latest_end_lsn | latest_end_time
-------+---------+------+-------+--------------+--------------------+-------------------------------+----------------+-------------------------------
16413 | sub1 | 2810 | | 0/145C3400 | |
2019-03-19 16:23:23.650073+00 | 0/145C3320 | 2019-03-19
16:23:23.446651+00

Issuing a refresh
stest=# alter subscription sub1 refresh publication with (copy_data =
false);
ALTER SUBSCRIPTION

resumes updates , but with a gap in data. Everything up-to to the refresh
statement is missing in the target.

What we're doing wrong ?

Thanks,
Radoslav