In zabbix server log is this message.

51238:20210307:172136.096 executing housekeeper
51238:20210307:172136.126 [Z3005] query failed: [0] PGRES_FATAL_ERROR:ERROR: invalid hypertable or continuous aggregate
[SELECT drop_chunks(1607361696,'history')]
51238:20210307:172136.127 cannot drop chunks for history
51238:20210307:172136.127 [Z3005] query failed: [0] PGRES_FATAL_ERROR:ERROR: invalid hypertable or continuous aggregate
[SELECT drop_chunks(1607361696,'history_str')]
51238:20210307:172136.127 cannot drop chunks for history_str
51238:20210307:172136.127 [Z3005] query failed: [0] PGRES_FATAL_ERROR:ERROR: invalid hypertable or continuous aggregate
[SELECT drop_chunks(1607361696,'history_log')]
51238:20210307:172136.127 cannot drop chunks for history_log
51238:20210307:172136.127 [Z3005] query failed: [0] PGRES_FATAL_ERROR:ERROR: invalid hypertable or continuous aggregate
[SELECT drop_chunks(1607361696,'history_uint')]
51238:20210307:172136.127 cannot drop chunks for history_uint
51238:20210307:172136.127 [Z3005] query failed: [0] PGRES_FATAL_ERROR:ERROR: invalid hypertable or continuous aggregate
[SELECT drop_chunks(1607361696,'history_text')]
51238:20210307:172136.127 cannot drop chunks for history_text
51238:20210307:172136.127 [Z3005] query failed: [0] PGRES_FATAL_ERROR:ERROR: invalid hypertable or continuous aggregate
[SELECT drop_chunks(1583601696,'trends')]
51238:20210307:172136.127 cannot drop chunks for trends
51238:20210307:172136.128 [Z3005] query failed: [0] PGRES_FATAL_ERROR:ERROR: invalid hypertable or continuous aggregate
[SELECT drop_chunks(1583601696,'trends_uint')]
51238:20210307:172136.128 cannot drop chunks for trends_uint
51238:20210307:172136.140 housekeeper [deleted 0 hist/trends, 0 items/triggers, 0 events, 1 problems, 0 sessions, 0 alarms, 0 audit, 0 records in 0.015441 sec, idle for 1 hour(s)]

In your documentation is not information about supported version TimescaleDB

https://www.zabbix.com/documentation/5.0/manual/appendix/install/timescaledb

TimescaleDB 1.7.4_1 is supported and work, but new instalation with 2.1.0 or upgrade have problem with Invalid hypertable or continuous aggregate.